borderline

A borderline personality or behavior refers to someone who exhibits traits that are close to being abnormal but not quite. Think of it like someone who's always teetering on the edge.

When we say something is borderline, we usually mean it's almost, but not quite, what we'd expect or consider normal. For example, if someone has a borderline personality disorder, they might have trouble controlling their emotions and behaviors, but they're still able to function in daily life. In other cases, we might talk about a borderline situation, like a job that's almost full-time but doesn't quite qualify as such. Or maybe we say something is borderline rude or off-color, implying it's just shy of being outright impolite or inappropriate.