pon·toon /pɑnˈtun/
  浮橋,浮筒,浮碼頭,潛水箱,二十一點(vt.)架浮橋于
  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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  pontoon
       n 1: (nautical) a floating structure (as a flat-bottomed boat)
            that serves as a dock or to support a bridge
       2: a float supporting a seaplane