fortification

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The science of fortifying.
• noun The act or process of fortifying.
• noun Something that serves to fortify, especially military works erected to fortify a position or place.

from The Century Dictionary.

• noun The act of fortifying or strengthening.
• noun The art or science of strengthening military positions in such a way that they may be defended by a body of men much inferior in number to those by whom they are attacked.
• noun That which fortifies, strengthens, or protects.
• noun Specifically A military work, consisting of a wall, ditch, palisades, etc., constructed for the purpose of strengthening a position; a fortified place; a fort; a castle.
• noun the polygonal or caponiere system
• noun the tenailled system, and
• noun the bastioned system. To these in modern times may be added the armored or turreted system. Mahan. Synonyms Fortification, Bulwark, Castle, Citadel, Fort, Fortress, Mamelon, Rampart, Redan, Redoubt. Fortification is the only one of these words that is used for the art or science, or for all classes of defensive works; the others represent kinds of fortification. Thus, fortress represents a large, and fort, generally, but not always, a smaller stronghold, defensible on all sides, as Fortress Monroe, Fort Sumter. See the definitions of the words.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of fortifying; the art or science of fortifying places in order to defend them against an enemy.
• noun That which fortifies; especially, a work or works erected to defend a place against attack; a fortified place; a fortress; a fort; a castle.
• noun Scotch pebble.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of fortifying; the art or science of fortifying places to strengthen defence against an enemy.
• noun That which fortifies; especially, a work or works erected to defend a place against attack; a fortified place; a fortress; a fort; a castle.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun defensive structure consisting of walls or mounds built around a stronghold to strengthen it
• noun the addition of an ingredient for the purpose of enrichment (as the addition of alcohol to wine or the addition of vitamins to food)
• noun the art or science of strengthening defenses