The boundary or distance around a body or figure.
All along the city's perimeter the guerillas kept up their attack night after night.
The perimeter of a prison is ringed with high walls and watchtowers, and the entire perimeter of Australia is bounded by water. To measure the perimeter of a square, multiply the length of one of its sides by four. Try not to confuse this word with parameter, which usually means a characteristic element or factor or a limit or boundary.