A wing of a building, notably in a church separated from the nave proper by piers.
A clear path through rows of seating.
A clear corridor in a supermarket with shelves on both sides containing goods for sale.
Any path through an otherwise obstructed space.
Seat in public transport, such as a plane, train or bus, that's beside the aisle.
An idiomatic divide between the Republican Party and the Democratic Party, who are said to be on two sides of the aisle.