| Fortress 1. (n.) A fortified place; a large and permanent fortification, sometimes including a town; a fort; a castle; a stronghold; a place of defense or security. 2. (v. t.) To furnish with a fortress or with fortresses; to guard; to fortify. Thesaurus Entries acropolis, bastion, beachhead, blockhouse, bridgehead, bunker, castle, citadel, donjon, fasthold, fastness, fort, garrison, garrison house, hold, keep, martello, martello tower, mote, motte, peel, peel tower, pillbox, post, rath, redoubt, safehold, strong point, stronghold, tower, tower of strength, ward |