courtesy of "the geek"
alee - adv. At or to the leeward side.
apparent wind - The combination of true wind and wind caused by the motion of a vessel.
backstay - n. Part of the standing rigging, a line or cable used to reinforce the mast by connecting the top of the mast to the stern of a vessel.
beam - n. The width of of a vessel at its widest point.
beam reach - Sailing with the wind approximately 90 degress off the vessel's centerline (abeam).
beating - v. Sailing almost into the wind.
before the wind - Sailing with the wind directly behind the vessel. Also known as running.
bow - n. The front portion of a vessel.
clew - n. The aft bottom corner of a sail.
COLREGS - (The International Regulations for Preventing Collisions at Sea, 1972) Rules of the road governing vessels operating on the high seas.
foot - n. The bottom edge of a sail.
"Hard a lee!" - Traditional command given by skipper or helmsman to indicate the start of a tacking maneuver. Refers to the action of pushing the tiller to the leeward side of the vessel which initiates the process.
head - n. 1) The top corner of a sail. 2) Sometimes used to refer to the forward end of a vessel (eg. A vessel that is trimmed poorly because it has taken on water or has too much weight forward, may find itself "down by the head").
hull speed - Maximum speed a hull can attain without planing. It is generally considered to be approximately equal to the square root of the vessel's waterline length multplied by 1.34.
in irons - Used to refer to a sailboat which has lost all speed because it is headed into (or close enough to) the wind.
"Jibe ho!" - Traditional command given by skipper or helmsman to indicate the start of a jibe maneuver.
knot - A unit used to describe the speed of boat or ship that is equivalent to one nautical mile per hour.
leach - n. The aft edge of a sail.
leeward - (loo-ward) adj. The side of a vessel, island, peninsula, etc. away from the wind.
line - General term for any rope or cable that is used on a boat, particularly the standing or running rigging on board a sailboat. (Remember: There are no "ropes" on a sailboat - only "lines"!)
luff - n. The forward edge of a sail. - v. Condition of a vessel or sail where the forward edge of the sail (luff) flaps and becomes less effective usually because the sail is trimmed in too far.
nautical mile - A unit of distance equal to 6080 feet used on boats, ships, and airplanes (compare to the statute mile).
planing - A situation in which a hull is supported by the hydrodynamic forces while moving through the water in addition to displacement buoyancy.
riprap - n. Large slabs of stone used as a protective barrier at the edge of a body of water.
running - Sailing with the wind directly behind the vessel.
sheet - Line used to control the angle of a sail with respect to apparent wind.
statute mile - A unit of distance equal to 5280 feet used on land (compare to the nautical mile).
tack - n. 1) The forward bottom corner of a sail. 2) A heading with respect to wind direction maintained by a sailboat. v. A turning maneuver where the bow of the vessel passes through the wind (also refered to as "coming about").