Someone who has been asked or was going to have sex for their first time but one way or another didn't. Also refer to cock-blocked.
1. Me and Amy were gonna have sex for the first time, at her party but then the cops came and ruined my chance.
2. George: So did you finally get laid?
Frank: No, her parents walked in as we were about to
George: Damn that sucks.
Frank: Yeah, I'm stuck being a theoretical virgin.