What does it mean to "have sex?" Well, it depends who you ask. Research has found that what people count as sex is all over the map.

For example, consider a 2015 study of heterosexual college students who were asked to determine whether each of 21 different intimate behaviors definitely was or wasn't sex. It turned out that there wasn't 100 percent agreement on anything. Though the vast majority agreed that both vaginal and anal intercourse constituted sex (especially when one or both partners had an orgasm), there were a minority who counted other acts, including oral sex, mutual masturbation, phone sex, nipple stimulation, and—yes—even deep kissing.

However, despite this wide individual variability, it's clear that most heterosexual adults agree that if you're having intercourse—vaginal or anal—you're probably "having sex."

But what about people who aren't heterosexual? Are there any widely shared beliefs about what counts as sex among folks who identify as gay, lesbian, or bisexual? A new set of studies published in the Journal of Sex Research attempted to answer this question and the results suggest that there is a "gold standard" when it comes to sex for gay and bisexual men, but not for sexual minority women.

In this paper, researchers reported the results of two studies in which self-identified LGB adults recruited at Pride festivals were surveyed about how they define sex. We're going to focus on the larger of the two studies, in which each gender group was asked to evaluate 16 to 17 potential sex acts. Men and women were, of course, asked about different intimate behaviors, due to anatomical differences.

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What they found was that, consistent with previous research on heterosexuals, there wasn't 100 percent agreement that any given behavior was definitely a form of sex. However, a clear difference emerged between sexual minority men and women with respect to how much agreement emerged in their ratings.

Among gay and bisexual men, the only two activities that a majority of participants endorsed as "definitely sex" were insertive and receptive anal intercourse (or "topping" and "bottoming" in colloquial terms). While there was more than 90 percent agreement that these things counted as sex, only about one-third were sure that things like oral sex, rimming, mutual masturbation, and insertion of dildos counted. Even fewer counted rubbing penises together or having phone sex.

By contrast, among lesbian and bisexual women, there were actually ten different acts that a majority of them endorsed as "definitely sex." The highest agreement (77 percent) was for using a double-ended dildo. This was followed by 69-ing, other uses of dildos, genital rubbing (also known as "scissoring"), oral sex, and mutual masturbation. Like the men in this study, only about one-third of the women counted rimming and far less counted phone sex.

One other interesting finding from this study that held for both men and women was that people were more likely to say that a given intimate behavior counted as sex if their partner had done it with someone else as opposed to if they themselves had personally done it. Previous research on heterosexuals has found the same thing.

Basically, what this means is that—regardless of gender and sexual orientation—we tend to judge our partners' behaviors differently than our own, likely in the interest of maintaining a certain image of the self. For example, if we can psychologically re-classify one of our previous experiences that was undesirable as "not sex," that might help us to feel better about ourselves and our sexual histories.

Overall, what this research tells us is that gay and bisexual men tend to have a much narrower view of sex compared to lesbian and bisexual women. In this regard, sexual minority men are actually a lot like heterosexuals given their widespread tendency to only count penetrative intercourse as "sex."

While sexual minority women also seem to have a bias toward counting penetrative activities (with dildos and fingers), they seem to take a much broader view, especially from the standpoint that they're the only group of adults that largely classifies oral sex as a form of sex.

These findings are important not just because they help us to better understand variability in how people define sex, but also because they may have healthcare implications. Given that people don't have perfectly uniform definitions of sex, healthcare providers would probably do well to ask patients about specific sexual practices, as opposed to focusing on generic and unreliable questions about whether they are "sexually active" or "having sex."