cheval-de-frise, chevaux-de-frise - defensive structure consisting of a movable obstacle composed of barbed wire or spikes attached to a wooden frame; used to obstruct cavalry

fortification, munition - defensive structure consisting of walls or mounds built around a stronghold to strengthen it

fortress, fort - a fortified defensive structure

line of defence, line of defense - defensive structure consisting of a barrier that can be employed for defense against attack

outwork - subsidiary defensive structure lying outside the main fortified area; "the outworks of the castle"

stronghold, fastness - a strongly fortified defensive structure

structure, construction - a thing constructed; a complex construction or entity; "the structure consisted of a series of arches"; "she wore her hair in an amazing construction of whirls and ribbons"