What does "aisle" mean?

Aisle: (a) A lateral division of a building, separated from the middle part, called the nave, by a row of columns or piers, which support the roof or an upper wall containing windows, called the clearstory wall. (b) Improperly used also for the have; -- as in the phrases, a church with three aisles, the middle aisle. (c) Also (perhaps from confusion with alley), a passage into which the pews of a church open.