The Collaborative International Dictionary of English v.0.48:

Extravaganza \Ex*trav`a*gan"za\, n. [Extravagance with an
   Italian ending: cf. It. stravaganza.]
   1. A composition, as in music, or in the drama, designed to
      produce effect by its wild irregularity; esp., a musical
      caricature.
      [1913 Webster]

   2. An extravagant flight of sentiment or language.
      [1913 Webster]

   3. a lavish or spectacular show or event, or presentation;
      as, Disney staged an extravaganza in Central Park that
      drew many thousands.
      [PJC]

WordNet (r) 3.0 (2006):

extravaganza
    n 1: any lavishly staged or spectacular entertainment

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "extravaganza":
   Grand Guignol, Passion play, Tom show, antimasque,
   audience success, ballet, blatancy, bomb, brazenness,
   broadcast drama, burlesque show, canard, charade, cliff hanger,
   closet drama, colorfulness, comedy drama, concoction,
   critical success, crudeness, dash, daytime serial, dazzle,
   dazzlingness, dialogue, documentary drama, drama, dramalogue,
   dramatic play, dramatic series, duodrama, duologue, epic theater,
   experimental theater, exposition, extravagance, extravagation,
   fable, fabrication, failure, fiction, figment, flagrancy,
   flamboyance, flashiness, flop, forgery, gaiety, garishness, gasser,
   gaudery, gaudiness, giveaway, glare, glitter, gorgeousness,
   happening, hit, hit show, improvisational drama, invention,
   jauntiness, jazziness, legitimate drama, loudness, luridness,
   masque, melodrama, meretriciousness, minstrel show, miracle,
   miracle play, monodrama, monologue, morality, morality play,
   music drama, musical revue, mystery, mystery play, myth,
   obtrusiveness, opera, pageant, panache, panel show, pantomime,
   pastoral, pastoral drama, piece, play, playlet, problem play,
   production, psychodrama, quiz show, radio drama, review, revue,
   romance, sensational play, sensationalism, serial, shamelessness,
   show, showiness, sitcom, situation comedy, sketch, skit, soap,
   soap opera, sociodrama, spectacle, spectacular, sportiness,
   stage play, stage show, straight drama, success, suspense drama,
   tableau, tableau vivant, talk show, tawdriness, teleplay,
   television drama, television play, theater of cruelty,
   total theater, variety show, vaudeville, vaudeville show, vehicle,
   vulgarness, word-of-mouth success, work