Someone who has had sexual intercourse (only counts if you've had sex once) but did not experience an orgasm due to a disturbance out of your control. The "O" that replaces the "I" in virgin stands for orgasm, the thing that was not experienced during intercourse.
Dude-One: Dude I lost my virginity last night to this bangin hot chick.
Dude-Two: How was it?
Dude-One: Oh it was great and all, but I didn't get to cum all over her face because deuschebag johnny came in and interuppted us.
Dude-Two: Dude... Dude... You may not be a Virgin anymore but you're still a Virgon. BRAH!