Source : Webster's Revised Unabridged Dictionary (1913)

Fortification \For`ti*fi*ca"tion\, n. [L. fortificatio : cf. F.
   fortification.]
   1. The act of fortifying; the art or science of fortifying
      places in order to defend them against an enemy.

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

   {Fortification agate}, Scotch pebble.

   Syn: Fortress; citadel; bulwark. See {Fortress}.

Source : WordNet®

fortification
     n 1: defensive structure consisting of walls or mounds built
          around a stronghold to strengthen it [syn: {munition}]
     2: the art or science of strengthening defenses
     3: the addition of an ingredient for the purpose of enrichment
        (as the addition of alcohol to wine or the addition of
        vitamins to food)