noun a wooden flat-bottomed boat, a metallic cylinder, or a frame covered with canvas, india rubber, ·etc., forming a portable float, used in building bridges quickly for the passage of troops.
2. pontoon ·noun a low, flat vessel, resembling a barge, furnished with cranes, capstans, and other machinery, used in careening ships, raising weights, drawing piles, ·etc., chiefly in the mediterranean; a lighter.