Definitions
1.nounAn area around the end of a bridge.
2.nounA fortification around the end of a bridge.
3.nounAn area of ground on the enemy's side of a river or other obstacle, especially one that needs to be taken and defended in order to secure an advance.
4.nounEither of the two atoms in different parts of a molecule that are connected by a bridge of two or more other atoms