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.
The act of judging or mocking someone due to their assumed lack of sexual experience. The perpetrator will normally base this assumption on the victim's personality traits or behaviors that they associate with being a virgin. The perpetrator will often do this cover up their own insecurities.