/ ˈbɔːdəlaɪn; NAmE ˈbɔːrdər-/ adjective , noun
■ adjective
not clearly belonging to a particular condition or group; not clearly acceptable :
In borderline cases teachers will take the final decision, based on the student's previous work.
a borderline pass / fail in an exam
■ noun
the division between two qualities or conditions :
This biography sometimes crosses the borderline between fact and fiction.