Your post on The Chastity Fallacy reminded me of a discussion I took part in once at a party. The guests were mostly lesbians and the topic was “How do you define sex?” For straight couples, “sex” is usually synonymous with “penis-in-vagina intercourse”. If a straight girl asks her friend if she and her new boyfriend have “had sex”, that’s usually what is meant.
This leaves a multitude of other sexual activities that are not considered sex in the strictest sense. Dry humping, heavy petting, fingering, hand jobs, and often oral sex are thought of as “messing around” and not “real sex”. This comes into play when people try to take inventory of their sexual past and figure out how many people they’ve “slept with”.
For lesbians, the line between “messing around” and “having sex” is almost non-existent. Lesbian sex doesn’t have to involve a strap-on or even penetration of any kind. Sexual activity that’s considered “messing around” for straight couples is “going all the way” for a lesbian couple.
I think at the end of the discussion, the best all-inclusive definition of “sex” we could come up was something like: “Stimulation of another person with intent to cause orgasm”. Note that nobody has to actually achieve orgasm, and neither party has to be naked at the time of the stimulation. Under this definition, humping another person’s leg while fully clothed would qualify as having sex.
If straight people counted even half of the things that lesbians consider sex, I suspect they’d have much higher sexual partner totals.