The ultimate definition of shit. When something is so preposterously shit, this can be used to express your disbelief and/or opinion.

Shitting - Not being serious, Joking, fooling, pissing around.

Chicago slang, means to be in agreement with something

The most adaptable word in the English dictionary

You can take a shit
You can say shit when your angry or frustrated
You can feel shitty
Be shitty
Act shitty
Look shitty
Give a shit

Or not give a shit
You can have shit
Throw shit

Hoard shit
Carry shit
Have to much shit
Have to little shit
Have no shit
Sling shit
Talk shit
Fight about shit
Fight shittily

Something you say at the end of your sentence for a varity of reasons. Being too lazy to finish your sentence and not having an actual verb in your sentence are common causes to throw in "and shit."
Also used to make things that aren't really as interesting as you had thought in your head seem cooler.

Sarcasm to something that is completely obvious.

Remaining in a bathroom stall until all other occupants of the bathroom leave, to avoid embarrassment of potentially loud shits.