A barrack is a building where military personnel live. It’s usually used in the plural, as barracks. It’s also a verb — when soldiers lodge in barracks, they barrack there.
Barrack comes from the Spanish barraca for "soldier's tent." Now it’s more than a tent. Barracks are the buildings where soldiers, commanders, and medical staff lodge. Many barracks are temporary buildings that can be taken down quickly and reassembled elsewhere. Other barracks are more sturdy and permanent, but the people who barrack (stay there) are always people in the military.