[1] : The Collaborative International Dictionary of English v.0.48

underworld \un"derworld`\, n.
   1. the lower of inferior world; the world which is under the
      heavens; the earth.
      1913 webster

            that overspreads with such a reverence
            this underworld.                      --daniel.
      1913 webster

   2. the mythological place of departed souls; hades.
      1913 webster

   3. the portion of the world which is below the horizon; the
      opposite side of the world; the antipodes. r.
      1913 webster

            fresh as the first beam glittering on a sail,
            that brings our friends up from the underworld.
                                                  --tennyson.
      1913 webster

   4. the inferior part of mankind. r. --atterbury.
      1913 webster

[2] : WordNet (r) 2.0

underworld
     n 1: the criminal class
     2: religion the world of the dead; "he didn't want to go to
        hell when he died" syn: hel, hell, hades, infernal
        region, netherworld, scheol
see also:
hel hell hades infernal region netherworld scheol 

[3] : Moby Thesaurus II by Grady Ward, 1.0

50 moby thesaurus words for "underworld":
   abaddon, black hand, cosa nostra, dis, gehenna, hades, hell,
   naraka, orcus, pandemonium, sheol, tophet, abyss, avichi,
   bottomless pit, bowels, criminals, deep space, deeps, depths,
   gangdom, gangland, gaping depths, hades, hell, infernal pit,
   infernal regions, inferno, jahannan, limbo, lower world,
   nether world, netherworld, organized crime, outer space, perdition,
   place of torment, purgatory, shades below, the mafia, the abyss,
   the bottomless pit, the grave, the mob, the pit, the rackets,
   the syndicate, the underworld, unfathomed deeps, unknown depths

Underworld >> U Words
Underworld, definition of term: Underworld
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