Skitz is a common slang for 'insane', though also a derogatory term for people with Schizophenia or any disorder under the Schizo-spectrum.
Insane: Skitz can be used to refer to someone acting crazy, which formed the term "Skitz out", which means to lose control: often via mental breakdown.
Schizophrenia: In this cade, Skitz also be used as a shortened version of the word "schizophrenic," though this usage is often considered derogatory and offensive, especially when used casually.
Example one:
Person 1: dude, you gotta help me.
Person 2: why, what happened?
Person 1: I dont know, (person 3) is totally skitzing out right now!
Example two:
Person 1: stop acting like a skitz, man, you're hearing things.
Person 2: that's really odd to say; don't use that word, asshole.
Used on the streets, if someone is skitz they are harsh and un-easy, not very friendly, to go skitz on someone is to bEat the shit outta them basically.
Tom - Hey that kid is staring
Billy - Fuck of you cunt, don't stare before i go fucking skitz on you.
Tom - thats better
Tom - hes staring again dude!
Billy - right thats it you cunt, *smack*
SKITZ.!!!!!!!!!!!!!!