pontoon

UK: /ˌpɒnˈtuːn/ US: /pɑnˈtun/ ,(pon to̅o̅n′)

WordReference Random House Learner's Dictionary of American English © 2026

pon•toon¹ /pɑnˈtun/  also pon•ton /ˈpɑntən/   n. [countable]

1. Military a floating structure used as support for a temporary bridge over a river.
2. Civil Engineering a float for a derrick, etc.
3. Nautical, Aeronautics, Naval Terms a seaplane float.

WordReference Random House Unabridged Dictionary of American English © 2026

pon•toon¹  (pon to̅o̅n′), n. 

1. Military a boat or some other floating structure used as one of the supports for a temporary bridge over a river.
2. Civil Engineering a float for a derrick, landing stage, etc.
3. Nautical, Naval Terms a float for raising a sunken or deeply laden vessel in the water; a camel or caisson.
4. Nautical, Aeronautics, Naval Terms a seaplane float.

Also, pon•ton  (pon′tn). 

• Latin pontōn- (stem of pontō) flat-bottomed boat, punt
• French ponton
• 1585–95

pon•toon²  (pon to̅o̅n′), n. [Brit.]

1. British Terms, Games the card game twenty-one.

• alteration of French vingt-et-un twenty-one 1915–20

Collins Concise English Dictionary © HarperCollins Publishers::

pontoon / pɒnˈtuːn/ noun

1. a watertight float or vessel used where buoyancy is required in water, as in supporting a bridge, in salvage work, or where a temporary or mobile structure is required in military operations
2. (as modifier): a pontoon bridge
3. a float, often inflatable, for raising a vessel in the water

Etymology: 17th Century: from French ponton, from Latin pontō punt, floating bridge, from pōns bridge

pontoon / pɒnˈtuːn/ noun

1. Also called: (esp US) twenty-one, vingt-et-un a gambling game in which players try to obtain card combinations worth 21 points

Etymology: 20th Century: probably an alteration of French vingt-et-un, literally: twenty-one