The Collaborative International Dictionary of English v.0.48:

Fair \Fair\, n. [OE. feire, OF. feire, F. foire, fr. L. fariae,
   pl., days of rest, holidays, festivals, akin to festus
   festal. See Feast.]
   1. A gathering of buyers and sellers, assembled at a
      particular place with their merchandise at a stated or
      regular season, or by special appointment, for trade.
      [1913 Webster]

   2. A festival, and sale of fancy articles. erc., usually for
      some charitable object; as, a Grand Army fair; a church
      fair.
      [1913 Webster]

   3. A competitive exhibition of wares, farm products, etc.,
      not primarily for purposes of sale; as, the Mechanics'
      fair; an agricultural fair.
      [1913 Webster]

   4. an exhibition by a number of organizations, including
      governmental organizations, for the purpose of acquainting
      people with such organizations or their members, not
      primarily for commercial purposes; as, the 1939 World's
      Fair.
      [PJC]

            Meet me in St. Louis, Louis
            Meet me at the fair
            Don't tell me the lights are shining
            Anyplace but there.                   --Song (1904:
                                                  words by
                                                  Andrew B.
                                                  Sterling,
                                                  music by Kerry
                                                  Mills,
                                                  popularized by
                                                  Billy Murray.
                                                  Prominent in
                                                  the movie
                                                  "Meet Me In
                                                  St. Louis",
                                                  1944)
      [PJC]

   After the fair, Too late. [Colloq.]
      [1913 Webster]