Pon·toon n.
 1. Mil. 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. Naut. 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.
 Pontoon bridge, a bridge formed with pontoons.
 Pontoon train, the carriages of the pontoons, and the materials they carry for making a pontoon bridge.
 Note: ☞ The French spelling ponton often appears in scientific works, but pontoon is more common form.

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