A childhood belief about virginity

When I was a child the only virgin I'd heard of refered to as such was the virgin Mary.
I also knew that Joseph wasn't yet her husband when she became pregnant (and nor was jehovah obviously).
Logically therefore a virgin must be an unmarried mother.
I continued to assume this until some idiot boys at school started asking all the girls if they were virgins (around ten years old I think) and it occured to me that none of us had children so it must be something else.