1. A fortification or outer defense to a city or castle, consisting of an elevation of earth about three feet high, along the foot of the rampart.

2. A fortress at the end of a bridge, or at the outlet of a city, having a double wall with towers.

3. An opening in the wall of a fortress through which guns are leveled and fired upon an enemy.

The French use the word also for an aperture in a wall to let in or drain off water; and the Spaniards, for a low wall round a church yard.