A Two-Shitter is someone who constantly one ups you on everything you say or do, usually being dishonest just to make themselves feel better or belittle you.
Name comes from the small example, "I took one shit, he took two shits"
"Man, Bob has been such a two-shitter lately. I can't say anything without him trying to prove he's better"
When you drop out of rotation after a couple hits because you're too lit to give a shit and it's time to call it quits.
I'm good man, that J's a two-shitter-quitter.