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
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"