Raz; from Raspberry-ripple, rhyming slang for Cripple or spacker. It can be used as a skit, a derogetory term, or a general insult to anyone doing something stupid.
"Jon you fucking Raz you just smoked my stash"
"oi james check out that Raz with no legs"
"Gary you Raz, you don't put fennel into creme Brulee!"
"Pass me the skangding you raz"