Meaning of twilight zone

twi'light zone"

Pronunciation: [key]
  1. the lowest level of the ocean that light can reach.
  2. an ill-defined area between two distinct conditions, categories, etc., usually comprising certain features of both; an indefinite boundary: a twilight zone between fantasy and reality.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.