The Collaborative International Dictionary of English v.0.48:

Orgy \Or"gy\, n.; pl. Orgies.
   A frantic revel; drunken revelry. See Orgies
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Orgy \Or"gy\, n.; sing. Orgies. [F. orgie, orgies, L. orgia,
   pl., Gr. ?; akin to ? work. See Organ, and Work.]
   [1913 Webster]
   1. A sacrifice accompanied by certain ceremonies in honor of
      some pagan deity; especially, the ceremonies observed by
      the Greeks and Romans in the worship of Dionysus, or
      Bacchus, which were characterized by wild and dissolute
      revelry. Usually in the plural form.

   Note: [The singular is rarely used in this sense.]
         [1913 Webster]

               As when, with crowned cups, unto the Elian god,
               Those priests high orgies held.    --Drayton.
         [1913 Webster]

   2. Wild, drunken, or licentious revelry; an uninhibited
      carouse. --B. Jonson. --Tennyson.
      [1913 Webster]

   3. A series of sexual activities involving more than two
      couples in a group.
      [PJC]

   4. Hence: An event characterized by unrestrained indulgence
      in passion; as, an orgy of buying of internet stocks.
      [PJC]

WordNet (r) 3.0 (2006):

orgy
    n 1: any act of immoderate indulgence; "an orgy of shopping";
         "an emotional binge"; "a splurge of spending" [syn: orgy,
         binge, splurge]
    2: secret rite in the cults of ancient Greek or Roman deities
       involving singing and dancing and drinking and sexual
       activity
    3: a wild gathering involving excessive drinking and promiscuity
       [syn: orgy, debauch, debauchery, saturnalia, riot,
       bacchanal, bacchanalia, drunken revelry]