'Underworld' definitions:

Definition of 'underworld'

From: WordNet
noun
The criminal class
noun
(religion) the world of the dead; "No one goes to Hades with all his immense wealth"-Theognis [syn: Hell, Hades, infernal region, netherworld, Scheol, underworld]

Definition of 'Underworld'

From: GCIDE
  • Underworld \Un"der*world`\, 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]

Synonyms of 'underworld'

From: Moby Thesaurus