Glossary of Nautical Terms & Abbreviations

• Aback  - describes a sail when the wind strikes it on it's lee side.
• Abaft   - towards the boats stern.
• Abeam   - at right angles to the centre-line of the boat.
• Aft   - at or near the stern.
• A-hull   - to ride out a storm with no sails set and the helm lashed to leeward
• AIS   - Automatic Identification System
• Amidships   - the centre of the boat, athwartships and fore-and-aft
• Apparent wind   - the direction and speed of the wind felt by the crew, it is a combination of true wind and that created by the movement of the boat.
• ARPA   - Automatic Radar Plotting Aid
• Astern   - behind the boat; to go astern is to drive the boat in reverse.
• Athwartships   - at right angles to the fore-and-aft line of the boat.
• Azimuth   - angular distance measured on a horizon circle in a clockwise direction, usually between an observer and a heavenly body

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• Back    when a wind backs, it shifts anti-clockwise.
• Back a sail    to sheet it to windward so that the wind fills it on the side that is normally to leeward.
• Backstay   a stay that supports the mast from aft and prevents its forward movement.
• Baggywrinkle   rope, teased out, plaited together and wound around stays, shrouds etc. to prevent chaffing.
• Ballast    extra weight, usually lead or iron, placed low in the boat or externally on the keel to provide stability.
• Ballast keel    a mass of ballast bolted to the keel to increase stability and prevent the boat from capsizing.
• Batten    a light, flexible strip, fed into a batten pocket at the leech of the sail to support the roach.
• Beam  (1) the maximum breadth of the boat, (2) a transverse member which supports the deck, (3) on the beam, an object is at right angles to the centre-line.
• Bear away   to steer the boat away from the wind.
• Bearing    the direction of an object from an observer, measured in degrees true or magnetic.
• Beat   to sail a zigzag course towards the wind, close-hauled on alternate tacks.
• Belay  to make fast a rope around a cleat usually with a figure of eight knot.
• Bend  (1) secure a sail to a spar before hoisting, (2) connect two ropes with a knot.
• Berth  (1) place occupied by a boat in harbour, (2) sleeping place on board.
• Bight  a bend or loop in a rope.
• Bilge  the lower, round part inside the hull where water collects.
• Block  a pulley in a wooden or plastic case, consisting of a sheave around which a rope runs. It is used to change the direction of pull.
• Boot-topping  a narrow coloured stripe painted between the bottom paint and topside enamel.
• Broach  when a boat running downwind slews broadside to the wind and heels dangerously. It is caused by heavy following seas or helmsman' error.
• Broad reach   the point of sailing between a beam reach and a run when the wind blows over the quarter.
• Bulkhead  partition wall in a boat normally fitted athwartships.

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• Cable  distance of measurement equalling 0.1 sea mile, 185 metres, 200 yards
• Centre-board   a board lowered through a slot in the keel to reduce leeway.
• Centre-line  centre of the boat in a fore-and-aft line.
• Chart Datum  reference level on a chart below which the tide is unlikely to fall. Sounding are given below chart datum. Datum level varies on country & area.
• Claw ring   a fitting, which slips over the boom like a claw, to which the main sheet is attached after reefing the sail.
• Cleat   a wooden, metal or plastic fitting around which a rope is secured.
• Clew   the after, lower corner of a sail where the foot and leech meet.
• Close-hauled   the point of sailing closest to the wind; see also beat.
• Close reach   the point of sailing between close-hauled and a beam reach, when the wind blows forward of the beam.
• Close-winded   describes a boat able to sail very close to the wind.
• Course   the direction in which a vessel is steered, usually given in degrees, true, magnetic or compass.
• Cringle   (1) a rope loop found at either end of a line of reef points, (2) an eye in a sail.

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• Dead run   running with the wind blowing exactly aft, in line with the centre-line.
• Deviation   the difference between the direction indicated by the compass needle and the magnetic meridian, caused by metal objects aboard.
• Displacement   (1) the weight of water displaced by a boat is equal to the weight of the boat;
• Displacement   (2) a displacement hull displaces its weight in water & is only supported by buoyancy.
• Downhaul   a rope fitted to pull down a sail or spar.
• Draft   the vertical distance from the waterline to the lowest point of the keel.
• Drift   (1) to float with the current or wind, (2) the distance a boat is carried by a current in a given time.
• Drogue   a sea anchor put over the stern of a boat or liferaft to retard drift.
• Drop keel   a retractable keel which can be drawn into the hull.

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• EPIRB  Emergency Position Indication Radio Beacon

• Fairlead - a fitting through which a line is run to alter the direction of the lead of the line.
• Fathom - the measurement used for depths of water and lengths of rope. 1 fathom = 6 ft = 1.83m
• Fiddle - a raised border for a cabin table, chart table etc. to prevent objects falling off.
• Fix - The position of a vessel as plotted from two or more position lines.
• Forestay - the foremost stay running from the masthead to the stemhead, to which the mainsail is hanked.
• Freeboard - vertical distance between the waterline and the top of the deck.

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• Genoa - a large headsail in various sizes, which overlaps the mainsail and is hoisted in light to fresh winds on all points of sailing.
• Gimbals - two concentric rings, pivoted at right angles which keeps objects horizontal despite the boats motion.
• GNSS - Global Navigation Satellite System
• Go about - to turn the boat through the eye of the wind to change tack.
• Gooseneck - the fitting attaching the boom to the mast, allowing it to move in all directions.
• Goosewing - to boom out the headsail to windward on a run by using a whisker pole to hold the sail on the opposite side to the mainsail.
• GPS - Global Positioning System
• Guard rail - a metal rail fitted around the boat to prevent the crew from falling overboard.
• Guy - a steadying rope for a spar a spinnaker guy controls the fore-and-aft position of the spinnaker pole; the foreguy holds the spinnaker pole forward.
• Gybe - to change from one tack to another by turning the stern through the wind.

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• Halyard - rope used to hoist and lower sails.
• Hank - fitting used to attach the luff of a sail to a stay.
• HAT - Highest Astronomical Tide
• Hatch - an opening in the deck giving access to the interior.
• Head-to-wind - when the bows are pointing right into the wind.
• Headfoil - a streamlined surround to a forestay, with a groove into which a headsail luff slides.
• Heads - toilets.
• Headway - the forward movement of a boat through the water.
• Heave-to - to back the jib and lash the tiller to leeward used in heavy weather to encourage the boat to lie quietly and to reduce headway.
• Heel - to lean over to one side.

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• IRPCS - International Regulations for Preventing Collisions at Sea
• Isobars - lines on a weather map joining places of equal atmospheric pressure.
• Jackstay - a line running fore-and-aft on both sides of the boat to which safety harnesses are clipped.
• Jury - a temporary devices to replace lost or damaged gear.

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• Kedge - a small, light second anchor.
• Keel - the main backbone of the boat to which a ballast keel is bolted or through which the centre-board passes.
• Ketch - a two-masted sailing vessel with a mizzen mast slightly smaller than the main and stepped forward of the rudder stock/post.
• Kicking strap - a line used to pull the boom down, to keep it horizontal, particularly on a reach or run.

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• Lanyard - a short line attached to one object, such as a knife, with which it is secured to another.
• LAT - Lowest Astronomical Tide - Chart Datum
• Leech - (1) the after edge of a triangular sail, (2) both side edges of a square sail.
• Lee Helm - the tendency of a boat to bear away from the wind.
• Lee shore - a shore onto which the wind is blowing.
• Leeward - away from the wind, the direction to which the wind blows.
• Leeway - the sideways movement off its course as a result of the wind blowing on one side of the sails and hull.
• List - a boat's more or less permanent lean to one side, owing to improper distribution of weight.
• Log - (1) an instrument for measuring a boats speed and distance travelled through the water. (2) to record in a book the details of a voyage.
• Luff - The forward edge of a sail. To luff up is to turn the boat's head right into the wind.

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• Marinized engine   an auto engine which has been specially adapted for use in boats.
• Mast step   the socket in the keel in which the base f the mast is located.
• Measured mile   a distance of one nautical mile measured between buoys or transits/ranges ashore, and marked on the chart.
• Meridian   an imaginary line encircling the Earth which passes through the poles and cuts at right angles through the Equator. All lines of longitude are meridians.
• Mizzen   (1) the shorter after-mast on a ketch or yawl
• Mizzen   (2) the fore-and-aft sail set on this mast.
• MHWN   Mean High Water Neaps
• MHWS   Mean High Water Springs
• MLWN   Mean Low Water Neaps
• MLWS   Mean Low Water Springs
• MMSI  Maritime Mobile Service Identity

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• Outhaul MHWN   a rope used to pull out the foot of a sail.
• Overall Length (LOA) MHWN   the boat's extreme length measured from the foremost part of the bow to the aftermost part of the stern excluding bowsprit, self-steering gear etc.

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• Painter   the bow line by which a dinghy, or tender is towed or made fast.
• Pay out   to let a rope put gradually.
• Point of sailing   the different angles from the wind on which a boat may sail, the boats course relative to the direction of the wind.
• Port   the left hand side of the boat looking forward.
• Port tack   a boat is on a port tack when the wind strikes the port side 1st & the main sail is out to starboard.
• Position line/line of position   a line drawn on a chart as a result of taking a bearing along which a boat's position must lie. Two position lines give a fix.
• Pulpit   a metal guard rail fitted at the bows of a boat to provide safety for the crew.
• Pushpit   a metal guard rail fitted at the stern.

• Quarter   the portion of the boat midway between the stern and the beam.

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• Range  (1) see transit.
• Range  (2) of tides, the difference between the high and low water levels of a tide.
• Range  (3) the distance at which a light can be seen.
• Reach  to sail with the wind approximately on the beam , all sailing points between running and close hauled.
• Reef  to reduce the sail area by folding or rolling surplus material on the boom or forestay.
• Reefing pennant  strong line with which the luff or leech cringle is pulled down to the boom when reefing.
• Rhumb line  a line cutting all meridians at the same angle, the course followed by a boat sailing in a fixed direction.
• Riding sail  s small sail hoisted to enable a boat to maintain steerage way during a storm.
• Rigging screw  a deck fitting with which the tension of standing rigging is adjusted.
• Roach  the curved part of the leech of a sail which extends beyond the direct line from head to clew.
• Run  to sail with the wind aft and with the sheets eased well out.
• Running rigging  all the moving lines such as sheets and halyards used in the setting and trimming of sails.

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• Schooner   a boat with two or more masts with the mainmast aftermost.
• Scuppers   holes in the toe rail which allow water to drain off the deck.
• Seacock   a valve which shuts off an underwater inlet or outlet passing through the hull.
• Sea room   room in which a boat can manoeuvre clear of land or other dangers.
• Set   (1) to hoist a sail.
• Set   (2) the way in which the sails fit.
• Set   (3) the direction of a tidal current or stream.
• Shackle   a metal link with a removable bolt across the open end, of various shapes D, U
• Sheet   the rope attached to the clew of a sail or to the boom, enabled it to be controlled or trimmed.
• Shrouds   ropes or wires usually in pairs, led from the mast to chain plates at deck level to prevent the mast falling sideways, part of the standing rigging.
• Skin fitting   a through-hull fitting where there is a hole in the skin through which air or water passes. A seacock is fitted for when the hole is not in use.
• Sloop   a single-masted sailing boat with one mainsail and one headsail.
• Spar   a general term used for any wood or metal pole, e.g mast or boom, used to give shape to sails.
• Spinnaker   a large, light balloon shaped sail used when reaching or running.
• Splice   to join ropes or wires by unlaying the strands and interweaving them.
• Spreaders   horizontal struts attached to the mast which extend to the shrouds and help support the mast.
• Stall   a sail stalls when the airflow over it breaks up causing the boat to lose way.
• Stanchion   upright metal post bolted to the deck to support the guard rails.
• Standing part   the part of a line not used when making a knot, the part of a rope which is made fast or around which the knot is tied.
• Standing rigging   the shrouds and stays which are permanently set up and support the mast.
• Starboard   right-hand side of the boat looking forward.
• Starboard tack   a boat is on a starboard tack when the wind strikes the starboard side first and the boom is out to port.
• Stay   wire or rope which supports the mast in a fore-and-aft direction, part of the standing rigging.
• Steerage way   a boat has steerage way when it has sufficient speed to allow it to be steered, or to answer the helm.
• Sternway   the backward, stern-first movement of a boat.
• Strop   a loop of wire or rope used to attach a block to a spar to make a sling.

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• Tack  (1) the lower forward corner of the sail.
• Tack  (2) to turn the boat through the wind so that it blows on the opposite side of the sails.
• Tacking  working to windward by sailing close-hauled on alternate courses so that the wind is first and one side then on the other.
• Tang  a strong metal fitting by which standing rigging is attached to the mast or other spar.
• Tender  or dinghy, a small boat used to ferry people and supplies from a yacht to shore.
• Tide  the vertical rise and fall of the oceans caused principally by the gravitational attraction of the moon.
• Toe rail  a low strip of wood or moulding running around the edge of the deck.
• Topping lift  a line from the mast head to a spar normally the boom which is used to raise it.
• Track  (1) the course a boat has made good.
• Track  (2) a fitting on the mast or boom onto which the slide on a sail fit.
• Track  (3) a fitting along which a traveller runs used to alter the tension of the sheets.
• Trim  (1) to adjust the angle of the sails, by mean of sheets so that they work most efficiently.
• Trim  (2) to adjust the boats load and thus the fore-and-aft angle at which it floats.
• True wind  the direction and speed of the wind felt when stationary at anchor or on land.
• Turn buckle  used to tighten the standing rigging.

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• Underway  a boat is underway when it is not made fast to the shore, at anchor or aground.
• Up haul  is a line to raise something vertically for example the spinnaker pole.
• Vang  see kicking strap
• Veer   (1) the wind veers when it shifts in a clockwise direction
• Veer  (2) to pay out anchor cable or rope in a gradual controlled way.

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• Wake    the disturbed water left astern of a boat.
• Weather helm    a tendency of a boat to turn into wind.
• Weather side    the side of the boat on which the wind is blowing.
• Whisker pole    a light pole used to hold out the clew of a headsail when running
• Winch    a winch is a mechanical device consisting usually of a metal drum turned by a handle around which a line is wound to give the crew more
  purchasing power when hauling taut a line.
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• Windage    those parts of a boat which increase drag for example rigging, spars, crew etc.
• Windlass    a winch with a horizontal shaft and a vertical handle used to haul up your anchor chain.
• Windward    the direction from which the wind blows toward the wind (opposite to leeward)

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• Yawl   a two-masted boat with the mizzen stepped aft of the rudder stock / post.

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