Datemate or Datefriend is a word used to describe that the person one is dating is non-binary. The term was created as a gender-neutral way to describe a non-binary significant other, replacing the “girl” in girlfriend and the “boy” in boyfriend with the word "date."
Similar terms include enbyfriend, joyfriend, theyfriend, partner, significant other, shipmate, and loveperson. Also see Gender-Neutral Terms.