(verb) the act of having diarrhea so badly that when you finish emptying your bowels it looks like you splatter painted the inside of the toilet bowl with feces.
"I think I must have eaten some bad fish tonight because I just Jackshit Pollocked that Shell bathroom."
Genuinely doing "jack shit" all day. "Jackshitting" is often referred to as "[procrastinating", but [procrastinating implies you actually have something to do, while you jackshit without having to have a life.
Susie: "James you wanna go paint drying?"
James: "Nah, I'm okay. I think I'll just jackshit here on the couch."
Susie: *sigh* "You're always jackshitting about."