borderline
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.”
Often used predicatively after 'be' or attributively before a noun. Frequently paired with 'on' (e.g., 'borderline on genius').
“Roland is a borderline alcoholic grammar pedant who is quite literally running from depression.”
From border + line.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.