barbican

{ } n. [ OE. barbican, barbecan, F. barbacane, LL. barbacana, barbicana, of uncertain origin: cf. Ar. barbakh aqueduct, sewer. F. barbacane also means, an opening to let out water, loophole. ] 1. (Fort.) A tower or advanced work defending the entrance to a castle or city, as at a gate or bridge. It was often large and strong, having a ditch and drawbridge of its own. [ 1913 Webster ]

2. An opening in the wall of a fortress, through which missiles were discharged upon an enemy. [ 1913 Webster ]