The Collaborative International Dictionary of English v.0.48:

Jamboree \Jam`bo*ree"\, n. [Etym. uncertain. Cf. Jambone.]
   1. A noisy or unrestrained carousal or frolic; a spree.
      [Slang] --Kipling.

            A Calcutta-made pony cart had been standing in front
            of the manager's bungalow when Raja Singh started on
            his jamboree.                         --W. A.
                                                  Fraser.
      [Webster 1913 Suppl.]

   2. a large festive gathering.
      [PJC]

   3. an assembly of boy scouts, usually at the national or
      international level, including camping among the
      activities; -- a term adopted by the Boy Scouts
      organization.
      [PJC]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "jamboree":
   Mardi Gras, Saturnalia, banquet, blowout, carnival, carouse,
   celebration, charivari, do, fair, feast, festival,
   festive occasion, festivity, fete, field day, fiesta, frolic, gala,
   gala affair, gala day, gathering, get-together, great doings,
   high jinks, jubilee, kermis, party, picnic, revelry, revels, spree,
   waygoose, wayzgoose