The Collaborative International Dictionary
Circumvallation \Cir`cum*val*la"tion\, n. (Mil.)
The act of surrounding with a wall or rampart.
A line of field works made around a besieged place and the besieging army, to protect the camp of the besiegers against the attack of an enemy from without.
Wiktionary
n. A rampart or other defensive entrenchment.
Usage examples of "circumvallation".
Though none of the earlier double circumvallations had to contend with relief armies of a quarter-million.
Land between the two sets of circumvallations, they huddled and took what was thrown at them for five days.
Starlight showed a rambling wall of circumvallation, with peaked roofs inside it.
Cape Diamond was now for the first time included within the line of circumvallation at Quebec.
Not only the gates, but the palisades must be got out, holes dug, and the circumvallation completed.
When the fleet of any nation actually beleaguers the port of its enemy, no other has a right to enter their line, any more than their line of battle in the open sea, or their lines of circumvallation, or of encampment, or of battle array on land.
The Volscians, under the leadership of Cluilius, the Aequian, were the first to come, and drew lines of circumvallation round the enemy's walls.
Then (as Jack the veteran reader of fortifications could see), as stealable objects, lootable churches, and rapable women had accumulated around this Amstel-Dam, those who had the most to lose had created Lines of Circumvallation.