A right minging bunter. Other words used could be swamp donkey or, of course, carrot cruncher! Normally a quasi will have a slight limp or will just walk abit funny (Like they've just shat themselves for example!)
"Bloody hell mate, look at that chick over there walking like a right noggin, wait a minute, is that a chick or a bloke?!"
"Jesus harry christ son, that ain't either, thats a bloody quasi!!"