(n.) A work projecting outward from the main inclosure of a fortification, consisting of two faces and two flanks, and so constructed that it is able to defend by a flanking fire the adjacent curtain, or wall which extends from one bastion to another. Two adjacent bastions are connected by the curtain, which joins the flank of one with the adjacent flank of the other. The distance between the flanks of a bastion is called the gorge. A lunette is a detached bastion. See Ravelin.

abatis acropolis advanced work balistraria bank banquette barbed-wire entanglement barbican barricade barrier bartizan battlement beachhead blockhouse breastwork bridgehead bulwark bunker casemate castle cheval-de-frise circumvallation citadel contravallation counterscarp curtain demibastion dike donjon drawbridge earthwork enclosure entanglement escarp escarpment fasthold fastness fence fieldwork fort fortalice fortification fortress garrison garrison house glacis hold keep loophole lunette machicolation mantelet martello martello tower merlon mote motte mound outwork palisade parados parapet peel peel tower pillbox portcullis post postern gate rampart rath ravelin redan redoubt safehold sally port scarp sconce stockade strong point stronghold tenaille tower tower of strength vallation vallum ward work