A person who was, at one point, a live-in boy/girlfriend who, due to one thing or another, has become an ex-boy/girlfriend. Due to the recession and price of housing, this person continues to share a bed with you as it is far far cheaper than finding a place of their own.
This situation is commonly found in twenty-somethings who have split up whilst cohabiting.
This relationship dynamic rarely involves sex, but is more comfortable than a "normal" friendship.
Guy number one: Hey, guy number two, how are things with your girlfriend?
Guy number two: Oh she's not my girlfriend any more, we're bedfriends now.