The act of someone putting their nose in their partner's asshole, and they fart, creating a dirtier alternative to motorboating.
Dude, I was totally motorboating this milf, and we wanted to take it to the next level. Meet asshole motorboating suckas!
(verb) To place nub between two breasticles and proceed to violently shake the appendage until the woman reaches climax.
Tommy really got Chelsea off with that amputation motorboating, the nubbing of her life.