fortification

Short definition from Wiktionary

Noun

1. 1
   The act of fortifying; the art or science of fortifying places to strengthen defence against an enemy.
2. 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.
3. 3
   An increase in effectiveness, as by adding ingredients.
4. 4
   A jagged pattern sometimes seen during an attack of migraine.