Barbican
Barbican ({not transcribed}) , noun
[Old English barbican, barbecan, French barbacane, Late Latin barbacana, barbicana, of uncertain origin: compare Arabic barbakh aqueduct, sewer. French barbacane also means, an opening to let out water, loophole.]
1.
(Fortification) 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.
2.
An opening in the wall of a fortress, through which missiles were discharged upon an enemy.
Also: Barbacan