Fortification .

a defensive wall or elevation, as of earth or stone, in a fortification.

an elevation raised above the main wall or rampart of a permanent fortification.

any low protective wall or barrier at the edge of a balcony, roof, bridge, or the like.

noun

barricade , barrier , bastion , buffet , buttress , defense , embankment , fortification , partition , protection , protective wall , rampart , safeguard , battlement , breastwork , bulwark , embattlement , railing , wall