'twilight zone' definitions:

The lowest level of the ocean to which light can reach

The ambiguous region between two categories or states or conditions (usually containing some features of both); "but there is still a twilight zone, the tantalizing occurrences that are probably noise but might possibly be a signal"; "in the twilight zone between humor and vulgarity"; "in that no man's land between negotiation and aggression" [syn: twilight zone, no man's land]