commonly shortened to "stack"
"She cleared like 3 stacks out of my straight shot.."
I don't wanna finish that stale smoke stack!
A sexual act, in which a man cums down his partner's throat, while he/she is deepthroating him. Often times the man holds his partners head from moving while doing this, so his partner does not "back off" untill the act is over.
The term may have come from the imaginary smoke that is likely to come from his partners ears afterward, or from the idea the the man's semen is the "smoke."