redoubt

a structure or place from which one can resist attack a massive stone redoubt at the entrance of the bay guarded the city Synonyms bastion, castle, citadel, fastness, fortification, fortress, hold, fort, strongholdRelated Words battlement, breastwork, bulwark, earthwork, embattlement, parapet, rampart; bunker, dugout; blockhouse, garrison house; alcazar, casbah (also kasbah)