Noah Webster
Circumvallation
CIRCUMVALLATION, noun
1. In the art of war, a surrounding with a wall or rampart; also, a wall, rampart, or parapet with a trench, surrounding the camp of a besieging army, to prevent desertion, and guard the army against any attempt of an enemy to relieve the place besieged.
2. The rampart, or fortification surrounding a besieged place.
[Note. This word, from the Latin, vallo, or vallum, vallus, denotes properly the wall or rampart thrown up; but as the rampart is formed by entrenching, and the trench makes a part of the fortification, the word is applied to both. See Eng. Wall.]