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]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "Pandemonium":
   Abaddon, Agapemone, Arcadia, Big Rock-Candy Mountain, Canaan,
   Cloudcuckooland, Cockaigne, Eden, Eldorado, Erewhon,
   Garden of Eden, Gehenna, Goshen, Hades, Happy Valley,
   Land of Youth, Laputa, Naraka, Never-Never-land, Neverland,
   New Atlantis, Quivira, Shangri-la, Sheol, Tophet, Utopia, avichi,
   cloudland, dreamland, dystopia, faerie, fairyland, heaven, hell,
   infernal regions, inferno, jahannan, kakotopia, kingdom come,
   land of dreams, land of enchantment, land of faerie,
   land of plenty, land of promise, limbo, lotus land, lower world,
   millennium, nether world, paradise, perdition, place of torment,
   promised land, purgatory, shades below, the abyss,
   the bottomless pit, the grave, the pit, underworld, utopia,
   wonderland



Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "pandemonium":
   Babel, Bedlam let loose, Gehenna, Sheol, Sodom, Tophet, abyss,
   agitation, babel, bedlam, blast, bluster, bobbery, brawl, broil,
   brouhaha, cacophony, cesspit, cesspool, chaos, charivari, chirm,
   clamor, clangor, clap, clatter, commotion, confusion,
   confusion of tongues, den, din, discord, disorder, disturbance,
   donnybrook, drunken brawl, dustup, ebullition, embroilment,
   fanaticism, ferment, flap, fomentation, foofaraw, fracas,
   free-for-all, frenzy, fume, furor, furore, fury, fuss, hades, hell,
   hell broke loose, howl, hubbub, hue and cry, hullabaloo, inferno,
   jangle, loud noise, netherworld, noise, noise and shouting, outcry,
   passion, perdition, racket, rage, rattle, rhubarb, roar, row,
   ruckus, ruction, rumble, rumpus, shindy, shivaree, static,
   storminess, sty, tempestuousness, thunder, thunderclap, tintamarre,
   tumult, tumultuousness, turbulence, turmoil, underworld, uproar,
   upset, wildness, zeal, zealousness



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.