Fortification /(?)/

For·ti·fi·ca·tion

Fortification

n.
  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.

Phrases & Compounds
Fortification agate
Scotch pebble.