society > armed hostility > defence > defensive work(s) > castle or fortified building > [noun] > tower or watch-tower > barbican (2)
An outer fortification or defence to a city or castle, esp. a double tower erected over a gate or bridge; often made strong and lofty, and serving…
The battlement of the outer fortification of a castle; the outer fortification, or barbican; a turret or watch tower on the outer wall.