The Collaborative International Dictionary of English v.0.48:

Aisle \Aisle\, n. [OF. ele, F. aile, wing, wing of a building,
   L. ala, contr. fr. axilla.] (Arch.)
      (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.
          [1913 Webster]

WordNet (r) 3.0 (2006):

aisle
    n 1: a long narrow passage (as in a cave or woods)
    2: passageway between seating areas as in an auditorium or
       passenger vehicle or between areas of shelves of goods as in
       stores [syn: aisle, gangway]
    3: part of a church divided laterally from the nave proper by
       rows of pillars or columns