DUCKUP, at sea, is a term used by the seafarers, when the main-sail, fore-sail, or sprit-sail, hinders his seeing to steer by a land mark: upon which he calls out, Duckup the clew-lines of these sails; that is, haul the sails out of the way. Also when a shot is made by a chase piece, if the clew of the sprit-sail hinders the fight, they call out, Duckup, &c.