QUEUE d'ARONDE, or Swallows Tail, in Fortification, a detached or outwork, the sides of which open towards the champaign, or draw closer towards the gorge. Single or double tenailles are of this kind, and some hornworks, the sides of which are not parallel, but narrow at the gorge, and open at the head, resembling a swallow's tail. When the sides are less than the gorge, the work is called centre queue d'aronde.