What is the meaning of Pontoon?

A flat-bottomed boat or other floating structure used as a buoyant support for a temporary bridge, dock or landing stage.

A bridge with floating supports.

A box used to raise a sunken vessel.

A float of a seaplane.

A lighter or barge used for loading or unloading ships.

A card game in which the object is to obtain cards whose value adds up to, or nearly to, 21 but not exceed it.

Source: wiktionary.org