borderline
adj. B2 Upper Intermediate US //ˈbɔɹdɝˌɫaɪn// UK //bˈɔːdəlˌaɪn// bor·der·line
adj. almost fitting into a certain category, but not quite. You use it when something is on the edge between two states, like being healthy and sick.
adj. situated on the edge of a category or condition; not clearly belonging to one side or the other. Often used with 'on' to indicate proximity to a limit.
His health is borderline, so he needs rest.
The company's profits were borderline, just enough to avoid a loss.
Her performance was borderline, hovering between acceptable and disappointing, leaving the judges unsure whether to award her a place in the finals.
From border + line.
Usage
Often used predicatively after 'be' or attributively before a noun. Frequently paired with 'on' (e.g., 'borderline on genius').