The act of taking a shit on the person while recieving a blowjob.
Comparable to a Blumpkin, but this act involves the poo to go on the person rather than the toilet.
It is a Human blumpkin.... hence, Humpkin
Only people who are disgusting do this lol... It a bit off from a Cleveland Steam Roller
Girl 1: I dont know what to get my bf for his birthday.
Girl 2: Just give him a blumpkin this year.
Girl 1: I did that last year, I need to up it
Girl 2: Give him a humpkin
Girl 1: A what?
Girl 2: Give him a blowjob and instead of him pooing in the toilet he'll poo on you.
Girl 1: That's a great idea!