Definition of "netherworld"

netherworld

noun
plural netherworlds
1. The place to which one's spirit descends upon death, conceived as below the surface of the earth.
  Quotations
  As Inanna prepares to descend she fastens the seven divine laws to her side, and as she walks toward the netherworld she speaks to her vizier, Ninshubur.
  1981, William Irwin Thompson, The Time Falling Bodies Take to Light: Mythology, Sexuality and the Origins of Culture, London: Rider/Hutchinson & Co., page 174
2. The locale of the spirit world or afterlife, whether deemed to be situated below the world of the living or not.
3. Specifically, a location of punishment in the afterlife; a hell.
4. (by extension) A hidden, shadowy, or sinister subculture, such as that of organized crime.