Situationship
A situationship is a relationship that sits somewhere between friendship and partnership — two people see each other regularly and share physical and emotional closeness, but never name a commitment or call it official. It lasts as long as the ambiguity works for both people, or until someone decides to define it or end it.
It differs from the talking stage in that physical and emotional intimacy are already happening — what's missing is agreement on what the two of you actually are.