countermure

Etymology
From.

Noun

 * 1) A wall raised behind another, to supply its place when that is breached or destroyed.

Verb

 * 1)  To fortify with a wall behind another wall.
 * 2) * 15??, Thomas Kyd, The Spanish Tragedy
 * They are plac'd in those empyreal heights, Where, counter-mur'd with walls of diamond, I find the place impregnable.