1. a flat-bottomed boat or hollow metal cylinder used to support a temporary bridge
Usage: engineering; military
2. one of the floats that supports a seaplane on water
Usage: aviation
3. a temporary bridge supported by pontoons

Examples

• The army engineers quickly assembled a pontoon bridge across the river.
• Each pontoon was carefully positioned to support the temporary crossing.
• The seaplane’s pontoons kept it afloat on the lake.
• Workers inflated the rubber pontoons before launching the boat.
• The pontoon bridge swayed gently in the current.
• They played pontoon late into the evening.
• The military used steel pontoons for the emergency bridge.