pontoon

/pɑnˈtun/
noun
  1. A flat-bottomed boat or floating structure used to support a bridge, platform, or other structure on water.
    • The army used a pontoon to help vehicles cross the river.
    • During the festival, a large pontoon was used as a stage on the lake.
    • The workers attached a new pontoon to the floating dock.
  2. A float or air-filled chamber that helps keep a boat, aircraft, or other object afloat.
    • The seaplane's pontoons allowed it to land smoothly on the water.
    • Each pontoon on the raft was made of sealed plastic.
    • The small boat had a damaged pontoon and started taking on water.
  3. A card game similar to blackjack, also called twenty-one.
    • Pontoon is a popular game in British pubs.
    • We spent the evening playing pontoon at the kitchen table.
    • She won three rounds of pontoon in a row.
Synonyms