1. (n.) The act of fortifying; the art or science of fortifying places in order to defend them against an enemy.

2. (n.) That which fortifies; especially, a work or works erected to defend a place against attack; a fortified place; a fortress; a fort; a castle.

abatis advanced work affirmation attestation authentication backing backing up balistraria bank banquette barbed-wire entanglement barbican barricade barrier bartizan bastion battlement bearing out bolstering breastwork bulwark buttressing case hardening casemate certification cheval-de-frise circumstantiation circumvallation confirmation contravallation corroboration corroboratory evidence counterscarp curtain demibastion dike documentation drawbridge earthwork enclosure enrichment entanglement escarp escarpment fence fieldwork fortalice glacis hardening invigoration loophole lunette machicolation mantelet merlon mound outwork palisade parados parapet portcullis postern gate proof proving proving out rampart ratification ravelin redan redoubt refreshment reinforcement reinvigoration restoration restrengthening revivification sally port scarp sconce stockade strengthening substantiation support supporting evidence tempering tenaille undergirding validation vallation vallum verification vitaminization work