An antestature is an archaic term for a fortification made of sandbags. They were historically hastily established by a retreating force to slow the progress of the enemy.
The word comes from the Latin ante ("before"), and statūra ("a standing").
This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed (1728). "Antestature". Cyclopædia, or an Universal Dictionary of Arts and Sciences (first ed.). James and John Knapton, et al.
The original article can be found at Antestature and the edit history here.