Meaning of twilight zone

Definition of twilight zone

(noun) 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"

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