According to this popular post on /r/facepalm, and again here
Some Mormon teens have convinced themselves that putting a penis in a vagina and then not moving is not sex. That's called soaking. Jump humping is when you get someone to jump on the bed next to you soaking to get some friction going without you technically causing the movement.
Is "soaking" and "jump humping" really a thing? Urban dictionary goes back to 2010 with a definition of "soak" that explicitly mentions Mormons.](https://www.urbandictionary.com/define.php?term=soak) Alpha House also mentions it.