The Collaborative International Dictionary of English v.0.48:

Gala \Ga"la\, n. [F. gala show, pomp, fr. It. gala finery, gala;
   of German origin. See Gallant.]
   Pomp, show, or festivity. --Macaulay.
   [1913 Webster]

   Gala day, a day of mirth and festivity; a holiday.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gala
    n 1: a gay festivity [syn: gala, gala affair, jamboree,
         blowout]