actually, after reading it again, it does sound like he meant a normal cowgirl position with a hint of femdom. At first I read "slides" as in "slip" which makes it sound very different. So I don't know, considering the other obvious mistake my guess is that english isn't his first language and so it came across completely different than what he had in mind. Because why would he suggest a tag that's basically a cowgirl position?

actually so funny LOL also fun fact, the OP also downvoted the suggestion after realizing the mistake lol jokes aside it did feel like an interesting tag. There's probably a better name/description for it though. I believe the OP meant "forcefully" as in "forced by gravity", so it shouldn't technically count as rape. It's more of a "lucky pervert" (or "rakki sukebe") situation which honestly should already be a tag it might've also been meant as actually willingly falling on top of the penis, which I don't remember ever seeing before, it also sounds like something dangerous to attempt, even in a doujinshi

Bro, are you describing cowgirl position or rape? Also, what do you mean "enters his penis"?

Enters his penis what?