jeferson starship

When a relationship has ascended beyond regular friendship, but has not evolved into a 'boyfriend-girlfriend' dating scenario. A term that can be used in place of more than friends. Not to be confused with jefferson starship

Sam: So, Craig. You and Vanessa dating now then?
Craig: Nah man, don't think so. We only been out once.
Chris: Wait, if you two aren't dating, what the hell are you?
Sam: You two must be Jeferson Starships then.