Unofficial Girlfriend
The term unofficial girlfriend is used to describe the female partner in the relationship when neither of the people in the relationship have made it official. The term unofficial girlfriend is used to show you intend to make said girl your girlfriend at some point. If you have an unofficial girlfriend you may act and speak as if she is your girlfriend but technically she is not. Exclusivity with unofficial girlfriends is optional, unlike with official ones.
“I will ask her out eventually but for now she is my unofficial girlfriend”