THRUM. Any coarse woollen or hempen yarn. It is used for mops, &c., in the cabins; also for mats, which are worked on canvas with a large bolt-rope needle.—To thrum. A vessel, when leaky, is thrummed by working some heavy spare sail, as the sprit-sail, into a thrummed mat, greasing and tarring it well, passing it under the bottom, and heaving all parts tight. The pressure forces the tarred oakum into the openings, and thus, in part, arrests the ingress of water.
THRUMMED MAT. A small mat faced with rope-yarn or spun yarn, which is used in a vessel's rigging to prevent chafing.
THRUST. The effort of a screw-propeller.
THUD. The sound of a bullet on hitting the intended object.
THULE [Gaelic thuath]. An extreme object to the north.
THUMB-CLEAT. In shape resembling a thumb. They arrest the topsail-reef-earings from slipping, and are also lashed to the rigging with a hollow, cut out to act as a hook, to suspend the bight of a rope, as the truss-pendants on the lower masts.
THUNDERING. A sailor's emphatic word for anything choice, large, fine, or powerful.
THUNDER SQUALL. This is similar to the black squall, only that it is always preceded and attended by lightning and thunder, and accompanied by extremely heavy rain.
THUNNY. See [Tunny].
THUS, Very well Thus, or Dyce. The order to the helmsman to keep the ship in her present direction, when sailing close-hauled. This truly sailor's motto was adopted by the Earl St. Vincent.