A crap word used by people who can't be arsed to think of better word for someone who is nearly an asshole, when they are one themself.
Tom:Oh my God you are such a borderline asshole!
Mike:You are such a boderline asshole for using that word!
An individual who is dangerously close to being known as and reffered to as an asshole.
Jake is a borderline asshole, only learning control his temper will save him.