Strictly, a three-masted vessel square-rigged on all three masts, or on three masts of a vessel with more than three. Hence a ship-rigged barque would be a four master, square-rigged on fore, main and mizzen, with spanker and gaff topsail only on the Jigger-mast. Generally now used to describe most medium or large vessels outfitted with smaller boats. As a consequence of this submarines may be larger than small ships, but are called boats because they do not carry boats of their own.