The Collaborative International Dictionary of English v.0.48:

Symposium \Sym*po"si*um\, n.; pl. Symposia. [L., fr. Gr.
   sympo`sion a drinking party, feast; sy`n with + po`sis a
   drinking. See Syn-, and cf. Potable.]
   1. A drinking together; a merry feast. --T. Warton.
      [1913 Webster]

   2. A collection of short essays by different authors on a
      common topic; -- so called from the appellation given to
      the philosophical dialogue by the Greeks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

symposium
    n 1: a meeting or conference for the public discussion of some
         topic especially one in which the participants form an
         audience and make presentations

Moby Thesaurus II by Grady Ward, 1.0:

140 Moby Thesaurus words for "symposium":
   Festschrift, airing, album, ana, analects, analysis, anthology,
   assemblee, assembly, assignation, at home, bacchanal, bacchanalia,
   bacchanalian, ball, bat, beauties, bender, binge, bout, brawl,
   bust, buzz session, canon, canvassing, carousal, carouse, caucus,
   celebration, chrestomathy, collectanea, collected works,
   collection, colloquium, commission, committee, compilation,
   complete works, compotation, conclave, concourse, conference,
   congregation, congress, consideration, conventicle, convention,
   convocation, council, dance, date, debate, debating, debauch,
   delectus, deliberation, dialectic, dialogue, diet, discussion,
   drinking, drinking bout, drunk, drunken carousal, drunkenness,
   eisteddfod, examination, exchange of views, festivity, fete,
   florilegium, flowers, forgathering, forum, garden, garland,
   gathering, get-together, gulping, guzzle, guzzling, housewarming,
   imbibing, imbibition, investigation, jag, joint discussion,
   lapping, levee, logical analysis, logical discussion, meet,
   meeting, miscellanea, miscellany, nipping, omnibus,
   open discussion, open forum, orgy, panel, panel discussion, party,
   photograph album, plenum, potation, prom, pub-crawl, pulling,
   quaffing, quorum, quotation book, rally, rap, rap session,
   reception, rendezvous, review, scrapbook, seance, seminar, session,
   shindig, sit-in, sitting, slipping, soiree, spree, study, swigging,
   swilling, synod, tasting, tear, toot, town meeting, treatment,
   turnout, ventilation, wassail