(On finding a dieting woman wolfing ice cream right out of the bucket while standing in front of the freezer at 2 am): "Are you whacking off in the tool shed again?"
A spontanious beating of the shaft. It is a very uncontrollable sensation. This is very common when one is hard.
Wayne: Man, my wacking shaft is really uncontrollable.
Courtney: That's understandable, wacking shaft happens to alot of guys i know.
Emily: Yeah, my brother had wacking shaft the other night
Phrase used to suggest a determined burst of action, similar to "Getting on with it" but with far more *gusto*.
In Maths Class:
person 1: OMG I'm sooo bored of division!
person 2: Okay, jeez, I know its long and hard but I'm just Wacking it out and I'll be done with it in a second. Don't be a fucking welp.
person 1: I guess you're right. Then we can use our free time to masturbate