When a girl gets on top of a man on his back, and slides her wet pussy on top his erect penis. It feels good for both sides because the girl gets her pussy rubbed and the man actually has the possibility of getting jacked off. It's literally the closest thing to sex without any possibility of cumming into the vagina.

It is worth noting to be at least a little careful though, to make sure nothing ricochets, or somehow it "slips" in the hole. Pussy sliding is fun, especially for the man, because he really doesn't have to do anything.

the art of remembering an arousing occurrence or some porn you watched while masturbating, often handy if you have no porn or your in the shower