rampart

A fortification consisting of an embankment, often with a parapet built on top.

A means of protection or defense; a bulwark. synonym: bulwark.

To fortify or surround with a rampart.

In fortification, an elevation or mound of earth round a place, capable of resisting cannon-shot, and having the parapet raised upon it; a protecting enceinte; also, this elevation together with the parapet.

Hence Something that serves as a bulwark or defense; an obstruction against approach or intrusion; a protecting inclosure.