Not doing anything or not doing anything important.
Andy: Hey, what's up?
Jake: I'm not doing shit.
Andy: Oh, same here.
An expression most commonly used when referring to performing a task, often used conversationally. Subsequently, often turned into a lame joke.
Joe: man, Mike is such a fucking lazy ass, he doesn't ever do shit.
Unfunny co-worker: oh he doesn't "douche it"? that's really unsanitary.
Joe: This is why I never talk to you.
To have sexual content that is more than just kissing, and implies all other bases other than first.
If you're horny, to an attractice person:
"Hey- wanna do shit?"
About your best friends who just did sexual things on your bed:
"They totally just did shit on my bed! Now I have to make them wash my skanky ass sheets!"
The act of being michevious when bored out of ones mind.
When Mike, Matt, and Logan were bored, the decided to do shit.
You're not going to do whatever it is you just threatened to do.
Chelsea: hoe I'mma steal your man if you don't back the fuck up
Sara: you aint gon do shit
Did you fuck her? Did you have sex with her?
Do that shit!