Oral sex isn't sex

How can one define sex? A (silly) definition would be: "the insertion of the penis into the vagina". Then again, that is the Collins English Dictionary definition, so maybe it's not that silly. Well, actually, the CED says it is followed by "thrusting motions" and culminates in orgasm. So who knows? I think that obviously, orgasm plays no part in defining sex. (N.B. the CED does not mention WHO orgasms.)

As I write this node, there is an avid discussion is the Chatterbox about this, about mormons and what not. DMan says oral sex isn't sex, and there seems to be a general acceptance to this. So lets take it a bit further:
Is anal sex considered sex? Most gay men would think so. Or can't gay men have sex? How about lesbians? Can you have sex with dildos? Or going down on each other? Where do we draw the line?
A girl recently asked me if just entering is considered sex. A tough one. Is it? Are two thrusts sex? Are 10? Is oral sex to orgasm sex? How about oral sex without orgasm?
I've heard of women who give oral sex freely and yet claim to be virgins. Well, maybe they are and maybe they're not.

I really wish I could sum up brilliantly, and give a resounding answer, but I can't. I just have to leave this question open.

But please feel free to add your opinions, as I would love it if this question was resolved.

Here are some definitions put forward by the Church as to what is or is not sex. Sexual intercourse, so pure sex, is exactly that, male and female genitalia doing what they were designed to do. This is the only type of "sex" per se. It should end with a male orgasm in the vagina. Any male orgasm outside the vagina is called Onanism and is a form of sodomy. Sodomy is specifically male ejaculation in another orifice besides the vagina. Therefore, there are two types: oral sodomy and anal sodomy.
Onanism comes from the story of Onan (Genesis 38:9-10) , who, upon the death of his brother, had to, under Jewish law, have intercourse with his sister-in-law. He did not want to have a child with her so he "pulled out" spilling his "seed" all over the earth.
Oral sex and anal sex are classified under foreplay or sexual deviance. Oral sex is permitted as foreplay between a married man and woman, if performed with solemnity and not abused. By abused I mean not occuring regularly as to take away from the love of the union, and concentrating on the lust of the act. Anal sex is strongly frowned upon because of the uncleanliness of going from the anus to the vagina in order for the man to have his proper orgasm.
The Roman Catholic Church strongly wishes that only true sexual intercourse ever occur, however under Catholic Moral Theology, Oral Sex is permitted as it is not objectively deemed a sin. As for virginity, as male/female genital sex is the only "true" form of sex, a man's or woman's virginity is intact if they refrain from this, however; the state of their soul has been jeapordized and must be cleansed due to the immoral practice of oral sex outside of marriage.