An outrage or swindle. Officially ‘a chiz is a swiz or a swindle as any fule kno’ (from the Molesworth series of books about school life by Geoffrey Willans). As a result of this the phrase "as any fule kno" has entered use on its own, especially in the letters pages of the British satirical/investigative magazine "Private Eye".
"Two quid for a glass of tapwater? What a chiz!"
or, in the original style:
"O no monday double maths alg trig ect chiz chiz. Pythagoras is uterly wet and i suspekt he keeps dolies at home".