DUCKUP, at sea, is a term used by the steer's-man, when the main-sail, fore-sail, or sprit-sail, hinders his steering to steer by a land-mark: upon which he calls out, Duckup the clew-lines of these sails, that is, hale the sails out of the way. Also when a shot is made by a chace-piece, if the clew of the sprit-sail hinders the sight, they call out, Duckup, &c.