Noun

• S: (n) garrison, fort (a fortified military post where troops are stationed)
• S: (n) fortress, fort (a fortified defensive structure)

Verb

• S: (v) fort, fort up (gather in, or as if in, a fort, as for protection or defense)
• S: (v) fortify, fort (enclose by or as if by a fortification)
• S: (v) fort (station (troops) in a fort)