Any short spar projecting from the hull of a ship or boat to allow a line to be extended beyond the hull; especially (a) each of two short spars that project from each side of the bow of a ship to extend the lower edge of the foresail to windward; (b) a similar spar used to extend the mainsail or mizzensail in the same way; (c) (later) a short spar extending aft from the stern, used to hold a backstay in place.