The Collaborative International Dictionary of English v.0.48:

Festival \Fes"ti*val\, a. [OF. festival, fr. L. festivum festive
   jollity, fr. festivus festive, gay. See Festive.]
   Pertaining to a fest; festive; festal; appropriate to a
   festival; joyous; mirthful.
   [1913 Webster]

         I cannot woo in festival terms.          --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Festi-val \Fes"ti-val\, n.
   A time of feasting or celebration; an anniversary day of joy,
   civil or religious.
   [1913 Webster]

         The morning trumpets festival proclaimed. --Milton.

   Syn: Feast; banquet; carousal. See Feast.
        [1913 Webster]

WordNet (r) 3.0 (2006):

festival
    n 1: a day or period of time set aside for feasting and
         celebration
    2: an organized series of acts and performances (usually in one
       place); "a drama festival" [syn: festival, fete]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "festival":
   Mardi Gras, Saturnalia, anniversary, banquet, birthday, blowout,
   carnival, celebration, commemoration, do, entertainment, fair,
   feast, festive occasion, festivity, fete, field day, fiesta, gala,
   gala affair, gala day, great doings, high jinks, holiday, holy day,
   jamboree, kermis, party, picnic, red-letter day, waygoose,
   wayzgoose