D defs.my
Entry 2 senses Webster, 1913

Pontoon

/pän-to͞on'/ · Pon·toon · IPA /pɒnˈtuːn/
01 n. A wooden flat-bottomed boat, a metallic cylinder, or a frame covered with canvas, India rubber, etc., forming a portable float, used in bui…
  1. 1.
    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.(Mil.)
  2. 2.
    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.(Naut.)
Phrases & compounds
Pontoon bridge — a bridge formed with pontoons.
Pontoon train — the carriages of the pontoons, and the materials they carry for making a pontoon bridge.