Rampart
/ˈɹæm.pɑː(ɹ)t/
noun
A defensive mound of earth or a wall with a broad top and usually a stone parapet; a wall-like ridge of earth, stones or debris; an embankment for defensive purpose.
A defensive structure; a protective barrier; a bulwark.
That which defends against intrusion from outside; a protection.
verb
To defend with a rampart; fortify or surround with a rampart.