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" - twilight zone
land that is unowned and uninhabited (and usually undesirable)
an unoccupied area between the front lines of opposing armies