A pivot working freely round in a socket. They are fitted in boats' bows, ships' tops and bulwarks, &c., for bearing small cannon of 1/2 lb. or 1 lb. calibre, which are worked by hand, and called swivels. Also, a strong link of iron used in mooring chains, &c., which permits the bridles to be turned repeatedly round, as occasion requires. Also, a swivel-link in chain-cables, made so as to turn upon an axis, and keep the turns out of the chain.