To tack: To go about from one tack to the other.
Tackle: A purchase composed of blocks and a rope, for multiplying power.
Tail block: A tackle consisting of two blocks, to one of which is attached a length of rope for fastening to any object at pleasure.
Taunt: Tall.
Taut: Tight.
Thwart: Athwart; across. The seat of a boat.
Tiller: The bar of wood or iron by which the rudder is worked.
Toggle: A pin placed through the bight or eye of a rope to secure it round a stay, mast, etc.
Top a boom: To raise one end of it by hoisting on the topping-lifts.