(v.) To relentlessly have sex with someone, as an analogy of the well-known scene in Forrest Gump where the main character runs across the US without having a break.
Person 1: Hey babe, I'm feeling so horny today that I think I could Forrest Hump you all night long, what you think?
Person 2: Fuck off!
(n.) High sex driven person who is capable of having a nearly endless sexual session without feeling tired
"Hey, I've heard that geeky nerdy weirdo from Maths class is such a Forrest Hump.. who would've thought right?!"