when the penis of one man is inserted into the anus of another man and then moved in and out with great force and speed so as to create a stimulus for both men
Sliding your butt cheeks over an exhaust pipe and having your friend rev the engine. Usually for self pleasure but was used 20 years ago as torture in Guantanamo Bay.
Jimmy: What the hell is that burningsmell...?
Andrew: I think its Daquan, him and his brother are blowbacking in his driveway.
The act of smoking a full joint/blunt, by oneself, in one sitting. References a scene in BoJack Horseman in which a very young BoJack is forced to smoke an entire cigarette.