Track ~ (1) The course a boat has made good. (2) A fitting (or integral slot) on the mast or boom into which the slides on a sail fit. (3) A fitting along which a traveller runs, used to control and tension the sheets.

Trampoline ~ The netting or fabric spanning the gap between the beams and/or hulls on the forward part of a multihull.

Transit ~ two fixed objects seen in line give a transit. Two transits give a position fix.

Transom ~ The transverse flat section that forms the stern-most part of a boat’s hull.

Traveller ~ (1) A fitting which slides in a track and is used to alter the lead of a sheet to the clew of a sail.

Triatic Stay ~ A back stay lead from one masthead to another, often fitted with insulators and used as a long-range radio antenna.

Trim, to ~ To adjust the angle of the sails to the wind by means of the sheets to optimise their efficiency.

Trimaran ~ A sailboat or any vessel with three hulls.

With no accommodation in the outside hulls, they're not as spacious below as a catamaran.

But these light displacement sailboats are quick - very quick!

The accommodation in a trimaran is no more than in a monohull of similar length.

Trim Tabs ~ Adjustable horizontal plates on the stern of a power boat which help control trim.

Trolling Line ~ A fishing handline streamed astern.

A trolling handline for fishing from a sailboat underway.

How to make one - and use it to good effect!

True Wind ~ The direction of the wind as felt at anchor or stationary.

Tumblehome ~ A unique seafaring word used to describe the section of a boat’s hull that curves upwards and inwards towards the centreline.

Turnbuckle ~ A rigging screw for adjusting the tension in standing rigging.

U...

Under Way ~ A boat is underway when she is not tied up ashore, on a mooring, at anchor or aground.

Uphaul ~ A line used to raise something vertically – the spinnaker pole for example.

V...

Vang ~ A tackle or other device between the mast and boom intended to hold the boom down, thereby controlling mainsail leech tension. See also 'kicking strap' or 'kicker'.

Veer ~ (1) To pay out anchor cable. (2) When the wind backs, it has changed its direction anti-clockwise.

W...

Wake ~ The trail of disturbed water left astern of a moving boat.

Warp ~ A rope used for anchoring or mooring.

Washboards ~ The boards that slot into place at the end of the companionway protecting the boat’s interior from a flooded cockpit and uninvited guests.

They're usually made from plywood, solid teak or fibreglass.

The sides of washboards should be only slightly vee'd or they'll fall out too easily.

Waterline ~ The line along the hull at which a boat floats.

Waterline Length ~ Often abbreviated to WL, the length of a boat from stem to stern at the waterline; a key factor in the the maximum hull speed that the boat can achieve in displacement mode.

Wear Ship, or Wearing Ship ~ An alternative to tacking, in which a vessel is gybed right the way around until the wind is on the other side of the bow. It was a necessary technique for old sailing vessels that were unable to tack through the wind, and was so called because of the 'wear and tear'often caused during the manouvre.

Weather (side) ~ The side onto which the wind blows.

Weather Helm ~ The tendency of a sailboat to come up head to wind.

Weigh Anchor ~ To raise the anchor, as in ‘Anchor’s aweigh!’

Wetted Surface Area ~ The area of the immersed portion of the hull.

Whisker Pole ~ A pole use to hold the clew of a headsail outboard when running downwind.

Widdershins ~ An old seafaring word which means to travel in a direction contrary to that of the sun.

Winch ~ A mechanical device - a geared drum – around which a rope (usually a sail or spar control line) is wound which then may be tensioned with a winch handle.

Windage ~ The amount by which a vessel is affected by wind. Also those parts of a boat that contribute to air drag, e.g. rigging, spars, superstructure etc.

Windlass ~ A mechanical device for hauling up the anchor. Can be electrical, hydraulic or manual.

Windward ~ Towards the direction from which the wind blows.

Windward Berth ~ A berth that a boat tends to be blown away from.

Wing and Wing ~ Sailing downwind with the foresail and mainsail set on opposite sides of the boat.

Also known as sailing 'goose winged', 'gull winged' or 'butterflying'.