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" पर्याय: no man''s land,
the lowest level of the ocean to which light can reach