Source : Webster's Revised Unabridged Dictionary (1913)

Erebus \Er"e*bus\, n. [L., fr. Gr. ?.]
   1. (Greek Myth.) A place of nether darkness, being the gloomy
      space through which the souls passed to Hades. See
      Milton's ``Paradise Lost,'' Book II., line 883.

   2. (Greek Myth.) The son of Chaos and brother of {Nox}, who
      dwelt in Erebus.

            To the infernal deep, with Erebus and tortures vile.
                                                  --Shak.

Source : WordNet®

Erebus
     n : (Greek mythology) Greek god of darkness who dwelt in the
         underworld; son of Chaos; brother of Nox; father of
         Aether and Day