1. The world of the dead.

2. A situtation in which one's status is uncertain, marginal, or undefined: “He was caught in the netherworld between the lowest levels of minor league baseball and the highest level of amateur play” (Tim Wakefield with Tony Massarotti). “She grew up in a kind of a class netherworld, not quite her father's daughter, not quite a servant” (Nina Sovich).

3. The part of society engaged in crime and vice: “Once they found themselves on the streets, they fell very quickly into the criminal netherworld” (Anne Applebaum).