batardeau

Etymology
From.

Noun

 * 1) A cofferdam.
 * 2)  A wall built across the ditch of a fortification, with a sluice gate to regulate the height of water in the ditch on both sides of the wall.
 * 1)  A wall built across the ditch of a fortification, with a sluice gate to regulate the height of water in the ditch on both sides of the wall.