borderline Definition

1. The border between one thing, country, etc and another.
2. A line dividing two opposing or extreme conditions.

Example: the borderline between passing and failing

1. On the border between one thing, state, etc and another; marginal.

Example: a borderline result
Thesaurus: marginal, uncertain, doubtful, ambivalent, indeterminate, problematic; Antonym: certain, definite.