The Collaborative International Dictionary of English v.0.48:

Pandemonium \Pan`de*mo"ni*um\, n. [NL., from Gr. pa^s, pa^n, all
   + dai`mwn a demon.]
   1. The great hall or council chamber of demons or evil
      spirits. --Milton.
      [1913 Webster]

   2. An utterly lawless, riotous place or assemblage.
      [1913 Webster]

   3. A condition of unrestrained disorder and chaotic, riotous
      uproar.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

pandemonium
    n 1: a state of extreme confusion and disorder [syn: chaos,
         pandemonium, bedlam, topsy-turvydom, topsy-
         turvyness]

The Devil's Dictionary (1881-1906):

PANDEMONIUM, n.  Literally, the Place of All the Demons.  Most of them
have escaped into politics and finance, and the place is now used as a
lecture hall by the Audible Reformer.  When disturbed by his voice the
ancient echoes clamor appropriate responses most gratifying to his
pride of distinction.