contravallation
noun
con·tra·vallation
¦kän‧trə+
plural -s
: a series of works confronting the walls of an invested place to isolate the defenders and safeguard the besiegers against sallies
also : construction of such works
Word History
Etymology
modification (influenced by Latin contra-) of French contrevallation, from contre- (from Latin contra-) + Late Latin vallation-, vallatio rampart, entrenchment