I. noun
an aboveground defensive structure that forms part of a fortification
the bulwarks were woefully undermanned
Synonyms: bastion, breastwork, parapet, rampart
Related Word: citadel, fort, fortress, stronghold
Contrasted words: bunker, dugout
II. verb
Synonyms: defend 1, cover, fend, guard, protect, safeguard, screen, secure, shield