a group of soldiers living in or defending a town or building, or the buildings that the soldiers live in

The 100-strong garrison had received no supplies for a week. 这支100人的守备部队已经一个星期没有得到补给了。

a garrison town 有驻防的城市

to put a group of soldiers in a place in order to live there and defend it

Troops are garrisoned in the area. 部队在这个地区驻防。