A fortress is a strong building or structure used for protection and defense.
Fortresses can be found in different places - they might be old castles perched on top of hills, military bases surrounded by walls and barbed wire, or even just a big house with high fences. Wherever you find one, its main purpose is to keep the people inside safe from harm.
A fortified place; a large and permanent fortification, sometimes including a town; for example a fort, a castle; a stronghold; a place of defense or security.
To furnish with a fortress or with fortresses; to guard, to fortify.
