crenel, crenelle - a notch or open space between two merlons in a crenelated battlement

fortress, fort - a fortified defensive structure

merlon - a solid section between two crenels in a crenelated battlement

bulwark, rampart, wall - an embankment built around a space for defensive purposes; "they stormed the ramparts of the city"; "they blew the trumpet and the walls came tumbling down"

construction, building - the act of constructing or building something; "during the construction we had to take a detour"; "his hobby was the building of boats"