I see virginity in two seperate ways: status as a captital-V "Virgin" and the progressive loss of levels of virginity with different activities.
My concept of a Virgin is someone who has never had sex with a partner. Sex with yourself does not count. Therefore, when someone has sex for the first time with the participation of someone else, whether it is oral, intercourse, mutual masturbation, whatever - that person is no longer a captital-V Virgin.
But after that, you can still loose your lowercase-v virginity with different activites that they've never done before. Anal virginity, oral virginity, strapping-on virginity, etc. You may have had sex, but you can still lose your lowercase-v virginity trying something new.
So yes, someone who has strapped it on with a partner is no longer a Virgin. But they can still have virginity to lose in other ways.