antemural

Century Dictionary and Cyclopedia

1. n. In medieval fortification, an advanced work defending the approach to a fortified place; a barbacan (which see). The term is sometimes applied to an exterior wall of a castle or fortress. See cut on preceding page.

Wiktionary

1. n. An outwork of a strong, high wall, with turrets, in front gateway (as of an old castle), for defending the entrance.

GNU Webster's 1913

1. n. An outwork of a strong, high wall, with turrets, in front of the gateway (as of an old castle), for defending the entrance.