Soir[e]e

from The Collaborative International Dictionary of English v.0.48

Soiree \Soi`ree"\, n. [F., fr. soir evening, fr. L. serus late,
   serum late time. Cf. {Serenade}.]
   An evening party; -- distinguished from levee, and
   matin['e]e.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

58 Moby Thesaurus words for "soiree":
      affair, assemblee, assembly, assignation, at home, ball, brawl,
      caucus, colloquium, commission, committee, conclave, concourse,
      congregation, congress, conventicle, convention, convocation,
      council, dance, date, diet, eisteddfod, evening, festivity, fete,
      forgathering, forum, gathering, get-together, housewarming, levee,
      matinee, meet, meeting, panel, party, plenum, prom, quorum, rally,
      reception, rendezvous, reunion, salon, seance, session, shindig,
      sit-in, sitting, sociable, social, social affair, social gathering,
      symposium, synod, turnout, wake