Please go to their website to further read on your subject. The below passage is copied verbatim from the site.

"What Does Virginity Mean?

Defining virginity can be confusing.For females, virginity used to be defined by an intact hymen. The hymen is located about a half-inch inside the vagina. Not all girls are born with hymens, which makes this definition of virginity somewhat misleading.Another definition of a virgin is a girl whose vagina has not been penetrated sexually.  The problem with this definition is that there are different ways of penetration.You may need to first figure out how you define "sex" before you define "virginity."  For instance, one person might think that any penetration of the vagina equals sexual intercourse. Other people restrict the definition of "sex" to penetration by the penis. Some people believe oral sex is "sex;" others disagree. These concepts depend on both emotional and physical factors. You have to determine what virginity means to you. Two more terms you should be familiar with are "abstinence" and celibacy."

"Abstinence" (based on the word "abstain") can refer to voluntarily giving up anything, including eating or drinking. In the context of virginity, abstinence refers to not having sex.

"Celibacy" specifically refers to sexual abstinence.  "Chastity" means almost the same thing as both "virginity" and "abstinence," but may be used in different contexts."

Etc...

To me my virginity has nothing to do with if you still have a hymen or not. To me virginity is different for everyone. Some people consider you losing your virginity when your hymen is broken which I honestly don't agree with it because a) some girls can be born without a hymen and b) a hymen can be broken in other ways besides sex (ie. tampons, during sports, horseback riding, etc). I believe a virgin is someone who hasn't participated in a mutual sexual act as in you both do something to each other. To be honest I see it differently for straight people, I think a straight girl is still a virgin until she has sex with a guy, she's still a virgin to me if she goes down on a guy and he goes down on her. It's really hard to explain and I hate when somebody tells me that I'm a virgin because I'm a lesbian and blah blah blah v.v. I just answer that virginity is different for people and my definition obviously differs from yours. It might sound stupid to people who don't understand that that I lost my virginity when I went down on a girl and she went down on me but not when a guy went down on me (ONCE) but virginity is more of a spiritual thing for me and not a biological one, if that makes any sense at all. So I do get frustrated when people tell me I must still be a virgin if I havne't had sex with a guy, but I'm used to people telling me who I am and how I feel all the time because they don't understand.

The heart has its reasons which reason knows not of.

ahahaah!!! no offense, no offense!!!

to me people loose their virinity when they enhance in any act that implies nudity and an apreciation of the genitalia that goes beyond textbook pictures...

as long as you touch it, smell it, lick it... put flowers on it ... whatever... it's sex to me

sex is not only penetration (though that's nice too)... but as long it's something a 5 year old wouldn't do (praise the lord)... and it's twisted, perverted and consensual and gratifying

yeah... that's sex

and that applies to EVERYBODY not only lesbians...

* I am the Cinnamon Spider *

When I recount to myself the girls I've had sex with I consider both oral and penetrative sex. When my girlfriend asks me how many people I've been with I only count oral sex because it brings my number down. (TMI)? 

Mom: Honey, how much did you pay for those shoes?

Me: Um, they were free, like two for one.

Mom: <Long pause> Sweetie...you got robbed.

I think virginity is more of a heterosexal concept than a homosexual one. If you need to define it, that's fine, but I don't think it's necessary. If you do define it, use what's most comfortable to you.

For me there are different stages of sex. You can have sex because you want satisfaction, you can have sex because you love someone, you can have sex because you are bored...
And I think it's the same with virginity.. Which has nothing to do with a penis in my opinion.. You can sleep with a boy and still feel like a virgin, or you sleep with a girl the first time and don't feel like a virgin anymore. In my opinion it has something to do with love and affection.
Maybe you sleep with a boy the first time of you life, because you're so drunk and don't remember most of it the next day..I don't think that you lost your virginity, you lost your dignity ;)
I hope you understand what I mean ;)

I think it's gone when your bare vagina comes into contact with any appendage of another person.

I once restricted it to the penetration definition: meaning if your vagina has been penetrated by an appendage.

Then I realized that oral sex is probably THE most intimate act.

So in a strict sense I would be hesitant to credit people who've engaged in oral sex, hetero or homo, as virigins. So, baarlijan_xen, I agree with you there.

Vero, I really disagree with your statement that a girl can sleep with a boy and still feel like a virgin - if that is her opinion (if she feels like she hasn't, I dunno, given herself over to a higher plane or whatever her definition is). If people know you've had sex and claim to be a virgin, others are going to laugh at you! Look, at the same time, I don't want to be insenstive here - there are girls who've been raped and they still claim their virginity... do we then define this as a consentual giving of yourself to an intimate carnal act? If that flies with you. So I'm a little hesitant to vocally persecute or draw virgin/not virgin lines between women who have sex. However, the bottom line is, I still feel that fondling, touching, licking, whatever, stimulating each other's genitalia is an act of sex, and claiming to be a virgin is erroneous.

In my endless pursuit of creating WTF? subject titles and sharing embarrassing life experiences I'm here to say that the hymen and penetration isn't a good indicator for losing one's virginity. You can break it with a tampon, or, for instance, flying down a partially snow covered hill at a speed that causes your sled to fly out from under you when it hits a rock and you land on said rock. At least it wasn't my head that hit the rock or I'd probably be a dead virgin.

IMO, virginity is lost when there is consentual genital stimulation with another person. And that includes the uhmm..stimulator as well as the stimulatee (makin' up words now). There are some women who are strictly on the giving side of sex, and I doubt they consider themselves virgins.

virginity is a state of being untouched, unexperienced, "pure", if you want to go that way.
with lesbians, i think virginity is lost when you engage in any sexual act, with someone else, with the intent to achieve orgasm.

by such metrics, mere kissing and masturbating by yourself are not included.