This is exactly my problem with the way people talk as well. We have too many different definitions for the word "sex". I know the difference between copulation and masturbation. We could look at the significance of virginity in terms of either one. As copulation goes, it's kind of a scientific question and easily defined. As assisted masturbation goes, it's more of a question of belief and relationships. What about solo masturbation? Could we consider a virgin someone who has never experienced orgasm? If we want to look at it from a spiritual point of view, how much does it take to defile someone's purity? one impure thought? I think it is possible to purify thoughts, but taking back an act or an experience is like trying to forget something that is indelibly imprinted on the mind.
I think everyone should get to define it for themselves. There's a lot of gray area and if you consider yourself a virgin (or otherwise) more power to you.
It's a bit arbitrary, but personally I would consider someone still a virgin if they've performed oral sex on someone else, but not if they've had it done to them. In less they tell me otherwise, in which case I'd go with their definition.