I'm a 14 year old girl and I hang out with my neighbor a lot (hes a guy) and one day we were at his house in the pool and we accidentally "rubbed" our bodies together and he got an erection. Was what we did a sex act? We still hang out and stuff but it hasn't been we kinda have that sexual tension between us now.
Was what you did a sex act? That's a wonderful question, Lolo, and I promise to answer it. I just need to say a few other things first. There are almost as many definitions of sex as there are people who've had it. Maybe even more!
Most people seem to think that the only "sex act" that matters is penis-in-vagina intercourse. Which obviously leaves not just a lot of activities out but also a lot of *people* out. The tricky part is that a lot of the time the emphasis is on the "'sex act' that matters", which sort of implies there are a lot of sex acts that don't matter. It's tricky exactly because a lot of the time it does matter. For instance when a husband who's been caught says "I did not have sex with that woman" even though they really had oral sex, or when teenagers tell their parents "we haven't had sex" when they mean they've done everything else.
For me I take what I hope is a more generous view and say that pretty much anything that two people do on purpose that arouses them is a sex act. For some people that could mean sexy text messages or email, for others that could be passionate kissing and grinding against each other, and for others it could be something as mild as holding hands.
One of the reasons I like to be generous about the definition is that it reminds us of all the other sexy, pleasurable, intimate things we can do with each other *besides* the infamous "sexual intercourse." Things we can do when we're not ready for more, things we can do when we don't have contraception handy, things we can do when we're still getting to know each other, and sometimes (a shock I know) things we can do that for many, many, many people feel a heck of a lot nicer than intercourse.
Another reason is that going the other way leaves a lot more room for slipperiness: "it doesn't count if I just stick it in." "It doesn't count unless you have an orgasm." "It doesn't count if he doesn't ejaculate." "It doesn't count if we just did oral stuff." "It doesn't count if we just did anal." It just seems like a lot more helpful to just say "yes, that all counts" and spend time quibbling instead over whether kissing hard or rubbing against each other counts.
And that's finally where I feel I can answer your question, Lolo. You said you rubbed your bodies together accidentally and he got an erection. That doesn't necessarily make it a sex act since men, especially young men, have a heck of a lot of erections a day anyway. If that's all there was to it, a bit of accidental contact that neither of you were really interested in repeating then no, it probably wasn't. On the other hand if it was something that interested or excited both of you, or if it's something one or the other or both of you would like to do again? Well, that's why I think this is a perfect question, because if you felt like you wanted to do it again this would be a great time to start having conversations about what you both want next time, what you're interested in, and especially what kind of limits or boundaries each of you has, and how you each expect the other to act when one of you feels your boundaries are being pressed.
And that's why I like a generous definition of what counts as sex.
By the way, here are two good Scarleteen posts about communicating about sex: