pontoon 1
/pon toohn"/ , n.
1. Mil. a boat or some other floating structure used as one of the supports for a temporary bridge over a river.
2. a float for a derrick, landing stage, etc.
3. Naut. a float for raising a sunken or deeply laden vessel in the water; a camel or caisson.
4. a seaplane float.
Also, ponton /pon"tn/ .
[ 1585-95; ponton ponton- (s. of ponto ) flat-bottomed boat, punt ]
pontoon 2
/pon toohn"/ , n. Brit.
the card game twenty-one.
[ 1915-20; alter. of F vingt-et-un twenty-one ]