1. flat-bottomed boats or hollow metal cylinders used to support a temporary bridge, platform, or floating structure
Usage: nautical; engineering
2. the floats attached to an aircraft to enable it to land on and take off from water
Usage: aviation

Examples

• The military engineers assembled pontoons to create a temporary bridge across the river.
• The floating dock was supported by large steel pontoons.
• Pontoons kept the seaplane stable on the water’s surface.
• Workers positioned the pontoons carefully before laying the bridge deck.
• The aircraft’s pontoons allowed it to land safely on the lake.
• Heavy pontoons were needed to support the weight of the construction equipment.