Afterguy: The spinnaker sheet that goes through the jaw of the spinnaker pole. Big boats usually attach a separate sheet and afterguy to both spinnaker clews. Since the afterguy takes more pressure than the sheet, the afterguy is a heavier line. Most of the time afterguys are simply called “guys,” not to be confused with the “foreguy” (see next page).
Abandon Ship: A command to leave a vessel due to imminent danger.
Abeam: A relative direction that is always at a right angle to the vessels direction of travel.
Aboard: Literally meaning to be “on board” a vessel.
Adrift: Afloat and detached from the shore or seabed, but not making way. Drifting with the wind or current.
Aft: Any portion of a vessel behind the centerline.
Aground: When a vessel is resting on the seafloor
Aloft: Refers to anything that might be above deck in the rigging or mast.
Anchor Light: A 360° white light displayed by a vessel at anchor.
Anchor Rode: A rope or chain specifically designed to hold a ship to its anchor.
Anchor: A metal hook-like device designed to attach to the seafloor in order to slow or stop a ship.
Anchorage: A designated area for boats to anchor in.
Apparent Wind: The velocity and direction of the wind in relation to an observer in motion.
Ashore: To be on land
Aspect Ratio: The height of a foil like a sail, keel, or rudder divided by its width. A high aspect sail has a long luff and short foot.
Astern: Towards the back of the vessel.
Auto-Bailer: A device that uses the suction created from forward momentum to drain water from the inside of a boat.
Backstay: A wire or rope used to support the mast from an attachment point at the stern of a vessel.
Bailer: A device used to remove water from the inside of a boat.
Bar: Mass of sand or mud formed by the movement of water which creates an area of shallow water.
Barge: A flat bottomed boat designed to carry heavy cargo, mainly through inland waterways.
Batten: A thin strip of material used to create rigidity and shape in sails or canvas.
Beam reach: Sailing at an angle approximately 90° to the apparent wind, such that the wind is crossing the vessel’s beam.
Beam: A measurement of the widest point of a vessel.
Bearing: The direction of a line between two waypoints.
Beating: Sailing in a zigzag course so as to make progress upwind.
Beaufort scale: A stepped scale defining wind strength, and its resulting effects, devised by Admiral Sir Francis Beaufort in 1808.
Becalm: A complete lack of wind, rendering sails useless.
Below: Any area of a boat below deck level. Downstairs.
Bend: Any type of knot used to join two lines together.
Bermuda rig: A sailing vessel designed with one tall mast and triangular sails.
Berth: (1) Sleeping accommodation on a boat. (2) A specified location for a boat when not at sea.
Bias Elongation: See Warp.
Bight: Any knot tied in the middle of a line.
Bilge: A compartment at the bottom of a vessel designed to collect water to be pumped out.
Bimini: A sunshade supported by a metal frame.
Bi-Radial: A sail construction technique where radial panels emanate from the head and clew. (See tri-radial.)
Bite: A rudder “bites” when water begins to flow past it, creating resistance and positive feel at the helm of a vessel.
Bitter End: The end section of a rope.
Blade: Slang term for a centerboard or rudder.
Block: A pulley
Boat hook: A pole with a hook on one end, designed to grab anything that might be outside the vessel. (generally dock lines, moorings, etc.)
Bobstay: A wire or rope designed to hold a bowsprit downwards; works in conjunction with the forestay.
Boom vang: A purchase system with the purpose of holding a boom down (nearer to head level). Also has the side effect of controlling the leach tension of a sail.
Boom: A spar designed to hold a sail outwards. Aptly named for the noise it’s known to make against the side of a sailors head.
Boomvang: A block-and-tackle or hydraulic ram that controls the angle of the boom. Lowering the boom tightens the leech of the mainsail.
Bosun’s chair: A canvas chair attached to a halyard, designed to hoist a person aloft.
Bow doinker: A small, but sometimes important device; designed to keep a sailboat crew from keelhauling their own sheet lines.
Bow line: A line employed at the bow, to hold a vessel to a dock or other structure.
Bow sprit: A spar protruding from the bow used to attach various rigging.
Bow: (1) The front most portion of a vessel. (2) Exactly one half of a dog’s bark.
Bowline: A very practical and strong knot.
Bridle: A length of wire or rope joined together at a midpoint; designed to distribute load in two or more directions.
Brightwork: Any varnished wood or polished metal found on a boat.
Bulkhead: A load bearing wall inside of a vessel. May or may not be watertight, depending on how old your vessel is.
Bullet: A first place victory in a sailing race.
Buoy: An anchored, floating object, which defines a given position. Used as an aid for navigation.
Burgee: A small triangular flag used to indicate membership to a particular yacht club.
Cabin: Refers to the interior living space of a vessel.
Capsize: When a boat overturns in the water.
Captain: A person whom is assigned command of a vessel.
Cat’s paws: Area of small ripples on the surface of the water, created by very light wind on an otherwise becalmed sea surface.
Catamaran: A sailing vessel with two hulls.
Catboat: A sailing vessel with one mast close to the bow, and a “gaff”‘ to support the sail.
Center of effort: The geometric center of force created by the wind on the sails. Subject to change based on sail shape and wind direction.
Centerboard: A board which pivots downward into the water in order to stop sideways slippage, and generate forward momentum by working in conjunction with the sails to create lift.
Centerline: An imaginary line drawn lengthwise through the center of a vessel.
Chafing: Any wear to running rigging or sails, created by unwanted friction.
Chain plate: Where standing rigging is attached to the hull of a boat.
Cheek block: A block designed to be mounted to the side of a surface.
Chine: A line formed lengthwise on the hull of a boat where two different angles meet.
Class: A group or classification of similar sailing vessels; see “one design”.
Cleat: A broad classification of devices used to secure a control line, sheet, or halyard on a boat.
Clew: The aft most corner of a triangular sail.
Clew: The back corner of a sail. On a mainsail the outhaul is attached to the clew; on genoas, the sheets are attached to the clew.
Close-hauled: Sailing as close to the true wind direction as possible.
Clutch: A set of jaws, similar to a cleat, designed to hold a rope fast under high loads.
Coaming: A raised lip or edge to prevent water intrusion near a hatch or porthole.
Coastal:  Of or referring to the coast.
Cockpit: The seating area of a small vessel toward which most of the controls are run.
Come about: To change direction through the wind.
Come to: To stop a vessel by turning into the wind.
Commodore: The chief officer of a yacht club. Commonly deals with more political issues than all of the combined nations on this planet.
Companionway: A raised hatch, with a ladder leading below deck.
Compass: A magnetic instrument which shows direction of travel in relation to Earth’s magnetic poles.
Constant bearing: When the angle of an approaching vessel remains the same over time, Indicating a collision course.
Corinthian: An amateur sailor, or sailing group.
Course: (1)The route to be taken around a buoy race. (2)The current direction of travel.
Crew: Any persons aboard a vessel whom are neither the skipper, nor passengers.
Crosscut: A sail construction technique where all the panels are parallel to each other and perpendicular to the sail’s leech.
Cunningham: A control that adjusts the position of the draft in a sail by changing the tension on a sail’s luff. The control is named after its inventor, Briggs Cunningham.
Cunningham: A line which provides downward force on the luff of a sail, in order to fine tune sail shape.
Daggerboard: A board pushed directly downward through the hull into the water: works in conjunction with the sails to provide forward momentum by creating lift, and minimizing sideways slippage.
Davit: A spar used to hoist a smaller dinghy, or tender, aboard a larger vessel.
Davy Jones’ Locker: An idiom referring to the bottom of the sea. Used as a euphemism for any person, shipwreck, or object lost to the sea.
Dead in the water: Used as a reference to a loss of power when previously underway.
Death roll: Slang term for a particularly epic capsize or wipeout. Especially when going downwind at speed.
Deck: The topside of the hull on which the crew works.
Dinghy: (1) A small sailing vessel, or (2) a small boat carried by a larger ship to act as a tender.
Displacement: The weight of a ship, as determined by the relationship between the mass and volume of the same weight in water.
Dock: A structure built over the water to which ships are secured.
Dodger: A hood over a hatch to protect from wind and spray.
Doldrums: A becalmed area in the Atlantic Ocean notorious for hurricane formation. Slang term sometimes referring to a similar becalmed area on a race course.
Downhaul: Any piece of line or rigging designed to apply downward force to a sail, spar, or blade.
Downwind: Point of sail 180° from the true wind direction.
Draft: (1) The depth of a vessel’s lowest point from the waterline.
Draft: 1. The deepest part of the curve in a sail. 2. The distance from the water line to the bottom of a boat’s keel.
Drifter: A sailing race in which there is no wind. Hence all boats are merely drifting.
E: The designation for the distance from the aft face of the mast to the outermost point on the boom to which the mainsail is pulled.
East: One of the four cardinal directions.
Ebb: Tidal movement out to sea.
Eddy: A current of water moving against the main flow. Often causes small whirlpools.
Elapsed time: Generally refers to the amount of time that has passed since the start of a sailing race.
Electrolysis: A small amount of electric current that passes between dissimilar materials. Causes corrosion on the spars and rigging of many sailing vessels where dissimilar materials are in constant contact.
Emergency tiller: A backup steering device used in the event of primary steering failure.
End for end: The act of reversing and re-splicing a halyard, sheet, or other running rigging in order to repair, or extend its useful lifespan.
Ensign: Nautical flag used to display a vessel’s country of origin.
EPIRB: (1) A distress beacon, triggered by a vessel in need of rescue. (2) Known in some circles as an “emergency pre-race beer”.
Even keel: Said when a vessel is sitting level to the surface of the water.
Eye splice: A fixed loop, or attachment point at the end of a line.
Fair: (1) Referring to a smooth curvature of a vessels hull. (2) To make a surface flush. 
Fairlead: A device used to keep a line running in the correct direction.
Fall off: To change direction so as to head more downwind.
Fathom: A unit of length used to measure depth, equal to six feet.
Feathering: Sailing a fine directional line between two points of sail, usually close hauled and irons.
Fend off: A command given to the crew to manually prevent the boat with colliding with something, usually at low speed.
Fender: A bumper designed to act as a cushion between a boat and the dock.
Fetch: The length of an area over water where waves are being generated by the wind.
Fid: A splicing tool designed to facilitate the making of various splices in rope or wire.
Fill Threads: See Warp.
Fixed propeller: A permanently mounted propeller protruding from the hull of a vessel.
Flattening Reef: A sail control that flattens the bottom part of the mainsail. It’s called a reef because the control line passes through a grommet on the leech of the sail about a foot above the boom. When the line is tightened, the grommet is pulled down to the boom and out as far as the sail can stretch. Also called “flattener”.
Flemish eye: A type of reeving eye in line, designed to facilitate in the installation of a halyard through a mast.
Foil: Can refer to either (1) The hydrodynamic “wing shape” of a sailing vessel’s keel and rudder, or (2) The thin, pliable, pieces of metal overtop of the forestay onto which a jib or headsail is attached.
Folding propeller: A type of propeller with blades that fold inward in order to reduce drag on a sailboat.
Following sea: Wave action that is traveling in the same direction as a ship.
Foot: The bottom edge of a sail.
Foot: The lowest edge of a sail.
Fore: Towards the bow.
Foreguy: The line that pulls the outboard end of the spinnaker pole down — not to be confused with the “afterguy.” 
Foresail: The forward most sail on a vessel.
Forestay: A line or cable attached from the bow to the mast, in order to provide structural support to the mast.
Foretriangle: The triangle formed by the forestay, forward edge of mast and foredeck.
Fouled: (1) Any entangled lines, rigging, or equipment. (2) An infraction of the rules in a sailing race.
Foulies: Slang term for foul weather gear.
Founder: Another word for sinking, or “to sink”.
Frame: Structural cross member of a ship’s hull.
Freeboard: The length hull exposed above the waterline.
Fully battened: Refers to a sail that has thin strips of batten across its entire width to provide better sail shape.
Furl: To roll a sail.
Gaff rigged: Any such vessel that is rigged using a gaff.
Gaff: A spar that holds the upper edge of a sail.
Galley: The kitchen
Gangplank: A mobile bridge to facilitate loading/unloading of persons and cargo onto a ship.
Gennaker: A type of lightweight crossover sail, designed to sail intermediate angles when neither a spinnaker, nor a Genoa would be suitable.
Genoa: A jib with a large overlap past the mast.
Gibe: See “gybe”
Gin-pole: A spar designed to facilitate raising and lowering the mast.
Glass: (1) A marine barometer. (2) Slang reference to fiberglass.
Global Positioning System: An accurate means of navigating via satellite based radio signals.
Gooseneck: The attachment point between the boom and mast. Allows the boom to move freely in any direction.
Gooseneck: The mechanical joint that connects the boom to the mast
Granny Knot: An incorrectly tied knot.
Gudgeon: One half of a fitting which attaches a ship’s rudder to her hull.
Gunwale: The upper edge of the hull, generally where the sides meet the deck.
Gybe (or jibe): To change direction through the wind.
Hail: A greeting designed to catch the attention of someone, often in reference to radio communication.
Half Hitch: A simple knot made around an object.
Halyard: The line on a sailboat used to raise, adjust, and lower sails.
Halyard: A line used to hoist or lower a sail.
Hand Held: A mobile marine communications radio.
Hank: A small fastener which attaches a sail to the forestay.
Harbor: A sheltered area of water where vessels may take refuge or dock.
Hard Over: A warning issued by the skipper, telling the crew that the tiller has been pushed hard over to one side Indicating that a sudden directional change is imminent.
Hard-chined: A vessel designed with a sudden change of angle lengthwise in the hull, usually placed near the waterline.
Hatch: A covered opening in a ship’s deck.
Hauling out: To crane a boat out of the water and place her “on the hard”.
Head to wind: Having the bow of a vessel pointed directly into the wind.
Head wind: A wind direction that is directly opposed to the direction of travel.
Head: The toilet or lavatory of a ship.
Head: The top corner of a sail
Header: A wind shift towards a vessel’s direction of travel, causing a turn to a more downwind course to correct for the shift.
Heading: A direction given in degrees on a compass or map.
Headsail: Any sail set forward of the mast.
Headstay Sag: The deflection of the headstay to leeward and aft caused by the force of wind on the sail. Because of the physics, no matter how tight your rigging, there will always be some sag in the headstay. I: The designation for the measurement of the height of foretriangle. Each rating rule has slightly different places which to measure from. J: The designation for the measurement of the base of the foretriangle, e.g., the distance between the mast and the forestay
Headway: Progress in a forward direction.
Heave to: A heavy weather technique designed to stop a vessel, but keep her pointed in the correct direction.
Heel: The sideways incline of a sailing vessel due to the force of the wind.
Helm: The steering mechanism of a ship, usually referring directly to the tiller or steering wheel.
Holding tank: The tank on a ship where sewage is held until proper disposal is possible.
Hull: The watertight shell and framework of a ship.
Hydrofoil: A wing like structure, or foil, capable of lifting the hull of a vessel out of the water at speed.
Icing: A serious weather condition where high winds combine with freezing temperatures, creating rapid ice accumulation on contact with any part of a ship.
Inboard: Can refer to anything situated within a ship.
Inclinometer: Instrument for measuring angle of slope, or heel on a sailing vessel.
Inflatable: Short for either a small “rigid hull inflatable” dinghy, or a type of personal floatation device.
Inland Rules: A specific set of maritime traffic laws applying to inland waterways.
Inlet: (1) A geographic feature that connects two bodies of water. (2) A fitting in a ship’s hull to allow seawater to enter or exit.
Inshore: Geographic area of water within a certain distance of land.
Intracoastal Waterways: A 3,000 mile stretch of navigable waterways, located in protected inland waters along the Atlantic and Gulf coasts.
Irons: When the bow of a boat is stuck into the wind, resulting in stalled sails and the inability to maneuver.
Isobars: Lines on a map connecting points of equal atmospheric pressure.
Jack lines: A line run lengthwise on the deck of a ship, onto which crew may clip a safety harness or tether. Reduces the risk of falling overboard.
Jenny: Slang term for a genoa sail.
Jetty: A man made wall of rock or rubble, intended to act as a barrier from the sea.
Jib Lead: The block or fairlead, through which the jib sheet passes, between the clew of the jib and the winch. The position of the lead has a great effect on the shape of the jib.
Jib: A triangular sail found at the front of a vessel.
Jibe: To change direction through the wind.
Jibe-ho: A warning issued before jibing a sailboat.
Jury rig: A makeshift repair. Often turns into a permanent repair on some vessels.
Keel: Fin like appendage protruding from the bottom of a sailing vessel that provides hydrodynamic stability and lift.
Keelhauling: A form of punishment at sea by which sailors were tied to a rope and dragged underneath the ship.
Ketch: A sailing vessel with two masts.
Kicker: Slang term for a type of rigid boom vang that can provide support to the boom when not underway. Eliminates the need for a boom topping lift.
Knock: Another term for header.
Knockdown: When a sailboat is suddenly pushed onto its side, either by an abrupt wind gust or rouge wave.
Knot: (1)A unit of speed equal to one nautical mile per hour. (2) A method of securing rope.
Laminated Sail Cloth: A fabric that has multiple (at least two) layers of fiber and film that have been permanently bonded by adhesive. The film provides the structure to control bias stretch. The fiber, in the form of woven material or unwoven yarn, provides stretch resistance in the fabric’s oriented direction. Also see “Scrim Cloth”.
Land lubber: A sailor’s term for anyone unfamiliar with the sea.
Laser: A small one design sailboat designed by Bruce Kirby.
Lateen rig: A triangular sail set on a long spar mounted at an angle to the mast.
Lay: The twist or braid of a rope or wire.
Layline: When zigzagging upwind, a layline is the last leg or bearing from which a vessel can reach her destination on a close-hauled course.
Lazaret: A storage locker towards the aft end of a boat.
Lazy Guy/Lazy Sheet: Lines used on big boats for jibing the spinnaker. Each clew of the spinnaker has a guy and sheet attached, the ones not in use are called the lazy guy and lazy sheet. 
Lazy Jacks: An arrangement of lines designed to cradle and stow a sail along the boom when not in use.
Leader line: A small diameter line used to pull a larger line through a mast, spar, or other rigging.
League: A unit of length equal to three nautical miles.
Lee Helm or Leeward Helm: The tendency of a boat to bear off when the helm is released. Lee helm is nor-mally encountered in light air or if your mast is too far forward in the boat. See “Weather Helm.”
Lee shore: Area of land downwind of a ship.
Leech: Aft most edge of a sail.
Leech: The back edge of a sail.
Leeward: Relative direction downwind from a point of reference.
Leeway: Amount that a ship slides to leeward
Leg: One segment of a sailing race or journey.
Length overall: The length of a vessel from one end to the other.
Lifeboat: A small craft carried on a ship for use in an emergency.
Lift: A force created by the flow of a fluid past an object.
Line: Correct nautical terminology for a rope.
LP: The abbreviation for Luff Perpendicular, which designates the shortest distance from the clew to the luff of a genoa. The size of genoas is expressed in a 54 percentage, which is the LP divided by J. For example, if a boat’s J measurement is 12 feet, a 150% genoa will have an LP of 18 feet.
Luff: 1. The forward edge of a sail. 2. The flapping of a sail caused by the boat heading too close to the wind or because the sail is not trimmed tight enough. 3. “Luffing” is altering your course toward the wind. In racing, luffing is a defense permitting a leeward boat to protect its wind from a boat passing to windward.
Luff: Forward most section of a sail.
Magnetic north: Direction that points towards the Earth’s magnetic pole.
Mainmast: Refers to the largest mast on a vessel with more than one mast.
Mainsheet: Primary control line for the mainsail. Has the greatest effect on sail trim.
Making Trees: Slang term for progress made against competitors in a sailing race.
Man overboard: An emergency signal indicating that someone has fallen into the sea.
Maritime: Anything relating to the sea.
Marlinspike: Rope working tool used for splicing and untying knots.
Mast: A spar, or pole, which supports the rigging and sails of a vessel.
Masthead: A platform or fixture at the top of a mast from which rigging, blocks, tackle, and lighting may be attached.
Midships: Referring to the middle section of a vessel.
Mizzenmast: A secondary mast placed behind the main mast.
Monkey’s fist: A specialized knot used to facilitate in the throwing of a line.
Mooring: Any permanent structure, or anchor, to which a vessel may be secured.
Mousing: As in, “mousing a shackle”; Method of securing a shackle pin or other rigging with seizing wire.
Narrows: The narrowest section of a navigable waterway.
Nautical mile: A distance corresponding to one minute of arc of latitude.
Navigation rules: The “rules of the road” that provide the means for organized maritime traffic.
Nun: A cone shaped navigational buoy.
Offshore: The geographical area of water away from the coast.
Old salt: Slang term for an experienced sailor.
One design: A system of racing sailboats in which all competing vessels are of equal design, construction, sail plan, rigging, etc.
Outboard: (1) Referring to anything outside of a vessel. (2) Referring specifically to an ‘outboard’ motor.
Outhaul: A line that controls sail shape, specifically the draft of a sail.
Outhaul: The control line that pulls the mainsail clew to the end of the boom, tightening the foot of the sail. 
Over tacking: Turning a sailing vessel through the wind, past the angle necessary to maintain a close-hauled course. Detrimental to making progress upwind.
Overpowered/Underpowered: A boat is overpow-ered when it heels too much from having too much sail up. Underpowered is when a boat is slowed because it does not have enough sail up. P: The designation for the measurement from the top of the boom at the gooseneck to the highest point on the mast that the mainsail will be raised.
Painter: A small diameter tow line attached to the bow of a dinghy.
Passageway: Any hallway found inside a ship.
Pennant: A triangular flag.
Personal floatation device: (PFD) Official term for a variety of life jackets.
Pier: A structure build overtop of the water, where vessels may dock.
Pilot: A person, or navigator, with specialized knowledge of a particular area.
Pintle: One half of a fitting designed to attach a rudder to a hull.
Piracy: An act of criminal activity on the high seas.
Pirate: Anyone who participates in piracy.
Pitch pole: A type of spectacular end-for-end capsize, in which the stern is catapulted over the bow.
Plane: When a vessel skims over the surface of the water rather than moving through it.
Point up: To change direction such that the bow is pointed more towards the wind.
Points of sail: Set of terminology that refers to the direction of travel in relationship to the wind.
Port tack: Sailing with the wind coming over the port side of the vessel.
Port: Left
Porthole: A window
Preventer: A sail control line that prevents accidental jibes.
Propeller walk: The tendency for a propeller to push a vessel sideways instead of forward or backward.
Propeller: A fan shaped apparatus that converts rotational force into forward thrust.
Purchase: The mechanical advantage gained from the use of line and pulleys
Radar: Short for radio detection and ranging. A system designed to send radio signals, and interpret their reflections as an image on a screen.
Rake: Measurement of fore/aft angle of a mast.
Rake: The mast’s inclination from vertical. The amount of rake is measured from the back of the mast at the partners to a plumb line hanging from the main halyard.
Ratchet block: A block that will spin in one direction, but not the other. Designed to provide friction in the loaded direction so as to make handling a line easier.
Rating: Refers to the PHRF handicap number assigned to a vessel.
Reacher: A high-clewed genoa used when reaching in heavy winds. Also know as a “blast reacher.”
Reaching: Sailing on a course at about 90° to the true wind direction.
Ready about: Warning issued to the crew, informing them that a tack or a jibe is in progress.
Reef: Method of temporarily reducing sail area.
Reeve: Act of running a line through a series of blocks.
Reeving eye: A type of eye splice designed to facilitate the reeving of a line through a mast, or series of blocks.
Regatta: A series of sailing races.
Rigging: The system of lines, spars, and hardware on a sailing vessel.
Roach: The area of a mainsail that protrudes beyond a straight line from the head to the clew. The roach is supported by battens.
Rode: An anchor line.
Rogue wave: A wave that is significantly larger than the present sea state, often coming from an unexpected direction of travel.
Roll: The side to side movement of a vessel.
Rudder: The part of a ship’s steering system that makes contact with the water.
Run: Point of sail approximately 160° from the wind direction.
Running rigging: The set of lines used to control sail shape.
Sail loft: A large flat space suited for working on sails.
Sail maker: A craftsman who works with sails.
Sail: A piece of fabric attached to a vessel such that it causes the wind to exert force on a vessel.
Scandalize: A method used to expediently reduce sail area, without properly reefing or furling.
Schooner: A sailing vessel with fore and aft masts of similar height.
Scow: A specific type of sailing dinghy characterized by a large sail plan, and wide beam.
Screecher: A crossover sail that is somewhere between a spinnaker and a genoa.
Screw: Another term for a propeller.
Scrim Cloth: An extremely loosely woven cloth. Lami-nated to Mylar, scrims make strong, lightweight sail cloths. Scrims are distinctive since there is empty space between threads.
Scud: Low lying clouds, particularly those observed in bad weather.
Scudding: A vessel carried along by a fierce storm.
Scull(ing): A method of providing forward momentum that involves rocking a boat from side to side, with synchronized movement of the rudder back and forth.
Scuttle: Method of sinking a ship a ship, usually by opening seacocks to flood the vessel with water.
Scuttlebutt: A drinking fountain found aboard a ship, slang for gossip.
Sea anchor: A canvas anchor deployed in deep water, designed to stabilize a ship in heavy weather by keeping her pointed into the wind and waves.
Sea state: Overall surface conditions of a large area of water.
Seacock: A specific type of valve that allows seawater to enter through the hull of a boat.
Sextant: A navigational instrument that uses celestial bodies (stars, planets etc.) to measure a ships latitude and longitude.
Shakedown cruise: A test voyage to measure the performance of a ship or her crew.
Sheet: A line used to control the shape of a sail in reference to the wind direction.
Shelf Foot: An option for mainsails that gives extra control to shaping the lower third of the mainsail. The name comes from the flat piece of cloth that connects the bottom of the sail to the boom.
Shoal draught: A ship with an unusually shallow draft, being able to navigate much shallower water than would be otherwise possible.
Shoal: An area of shallow water.
Shroud: The lines or cables that hold a mast up from the sides.
Shroud: Wires that support the mast athwartships.
Signal flag: A flag that is representative of a letter, word, or some other semantic meaning.
Sinking: Present participle of the verb “to sink”, of which it is common knowledge among sailors that all boats are sinking, some merely faster than others.
Skeg: A downward projection from the hull that protects the rudder from damage.
Skiff: A lightweight, high performance sailing dinghy, capable of easily planing across the water at high speeds.
Skipper: Another word for the captain of a ship.
Slip: A designated space for a boat to dock in.
Sloop: A medium sized sailboat with one mast, and sails fore and aft.
Sonar: A device that uses sound to range and image underwater objects.
Sou’wester: A storm that approaches from the southwest.
Spar: Any pole that supports a sail.
Spinnaker pole: A spar deployed to help control a spinnaker,
Spinnaker: A large downwind sail.
Splice: A method of joining two lines together, or creating an eye at the end of a line, by unraveling the braid and recombining into one continuous piece.
Spreader: A spar used in conjunction with shrouds to help stabilize the mast.
Spreader: Strut attached to the side of the mast, which amplifies the shrouds ability to support the mast.
Spring line: A line securing a vessel to a dock, particularly one that prevents fore and aft movement.
Squaring the Pole: Tightening the afterguy, which pulls the spinnaker pole back.
Stanchion: A short vertical pole through which life lines are run to keep crew from falling overboard.
Standing rigging: A system of line or wire that is designed to support the mast, and is not normally adjusting while under sail.
Starboard tack: Sailing with the wind coming over the starboard side of the vessel.
Starboard: Right.
Stay: Similar to a shroud, a part of the standing rigging that helps support the mast.
Stay: Wires that support the mast fore-and-aft, e.g.,”forestay” and “backstay.” Also see “Shroud.”
Staysail: A sail attached to a forestay, usually smaller than a jib or genoa.
Steaming light: A light displayed at night, indicating that a sailing vessel is under motorized power.
Steerage: Act of steering a vessel.
Stopper knot: A knot that keeps a line from passing through a hole or block.
Stow: To put away or store in such a way as to make seaworthy.
Sunfish: A popular, beach launched sailing dinghy with a lateen rig.
Tack: 1. The lower forward corner of a sail. 2. Turning the boat so that the bow passes through the eye of the wind. 3. (Port or Starboard) You are sailing on starboard tack when the boom is on the port side and vice versa.
Tack: The forward most corner of a sail.
Tacking duels: A series of complex maneuvers between two boats tacking to windward, with the end goal of gaining an aerodynamic advantage over a competitor.
Tacking: A zigzag course to achieve a net upwind direction.
Tape-Drive ® : The patented sail construction system used by UK Sailmakers, which uses high strength Kevlar tapes to lock in a sail’s designed shape. The tapes radiate from the three corners of the sail along computer-mapped load lines.
Tell-tale: Small strip of yarn or fabric attached to a sail, used as an indicator of air flow.
Telltales: Streamers attached to the sail to indicate wind flow. Tri-Radial: A sail construction technique where radial panels emanate from all three corners of the sail. (Also see bi-radial.)
Thwart: A bench seat.
Tiller extension: An extension attached to the tiller to aid in gaining better helm feel, and body positioning.
Tiller: A lever attached to the rudder used for steering.
Tonnage: The total weight of a vessel.
Topping lift: A line designed to hold a spar aloft.
Transom: The aft most wall, or bulkhead of a vessel.
Traveler: A fitting that slides from side to side on a line or track. Commonly used as an attachment point for the mainsheet.
Trim: Small adjustments made to sails in order to maximize their efficiency.
Trimaran: A sailing vessel with three hulls.
True north: The direction towards the Earth’s geographic north pole.
Turnbuckle: Two threaded bolts encased within a frame, used to put tension onto a vessels standing rigging.
Turning turtle: A full 180° capsize, when a vessel’s mast is pointed directly towards the bottom of the sea floor.
Upwind: The direction towards which the wind is coming from, from a given reference point.
Vang: Slang for boom vang.
Vessel: Any craft designed for movement through or on the water.
Wake: Turbulent water left behind a vessel in motion.
Warp, Fill and Bias: Woven cloth has threads running in two directions. Fill threads run perpendicular to the longest side of the cloth and warp threads are parallel to the longest edge of the cloth. The strength of woven cloth lies only in the direction of the threads. Stresses not parallel to the threads are called bias stresses. The farther off the thread line the stresses are, the greater the distortion of the cloth. Bias stresses at 45 degrees to the threads distort the sail the most.
Warp-Oriented Cloth: Sail cloth that has more strength in the warp direction than in the fill direction. Extra strength is created by more or stronger threads run-ning in the warp direction. Some extreme warp-oriented laminates have no fill yarns. Instead, yarns are just glued to the Mylar film in the warp direction. These extreme warp-oriented fabrics rely on the Mylar for strength in all other directions.
Wash: Waves created by a vessel in motion.
Waterline: Where the hull of a ship meets the surface of the water.
Waypoint: An intermediate point defined by a set of navigational coordinates.
Weather or Windward Helm: The tendency of a boat to head up when the helm is released. Weather helm is measured in degrees of angle that the rudder must be turned to sail a straight course. See “Leeward Helm.”
Weigh anchor: To pull up an anchor.
Wetted area: The surface area of a hull immersed in water.
Wheel: An alternative steering device to a tiller, usually found on larger vessels.
Whisker pole: Spar used to hold a large jib or genoa outboard when sailing downwind.
Windage: Net wind resistance of a boat.
Windlass: A winch mounted on a horizontal axis used to weigh anchor on larger vessels.
Windward: A direction upwind from a point of reference.
Yacht: A recreational vessel, usually of intermediate to large size.
Yawl: A two masted sailing vessel, specifically with the aft mast behind the helm.