Pon*toon" (?), n. [F. ponton (cf. It. pontone), from L. ponto, -onis, fr. pons, pontis, a bridge, perhaps originally, a way, path: cf. Gr. &?; path, Skr. path, pathi, panthan. Cf. Punt a boat.] 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.

&fist; The French spelling ponton often appears in scientific works, but pontoon is more common form.

• Latin pons "bridge"
  
• French vingt-et-un "twenty-one"
  
• A floating structure used as a support for a temporary bridge.
  
• A floating structure used as a bridge or dock.
  
• A box used to raise a sunken vessel.
  
• A float of a seaplane.
  
• (Card games): A card game in which the object is to obtain cards whose value adds up to, or nearly to, 21 but not exceed it.