1) Another word for "fiesty".
2) A word used when you have no other word to describe someone or something, usually used to piss someone off.
3)Anything you want it to mean.
"Maria, you need to chill out, you're being a little shiesty today."
When someone is 'shistey' it refers to a shit head being extra shit headish; sometimes the intensity one can become can escalate to an emotional/personal level and the person can become ButtHurt.
(Often used in the succession "shistey cunt" or "shistey bitch")
Hey, how was work with that shit head Connor?
Slow, but he was being extra dickish. Shiesty cunt.