A way of saying Cheers, and Boy in one word. A few rules of "Cheboi" is it should ALWAYS be said in a raised voice, and the correct pronounciation is "Cheeryoi!!!!!" the exclamation marks are to emphasize it should be shouted.
Mum: Junior, dinners ready...
Mum: You fucking what? Your no son of mine!"
Andy: I can't be arsed to go out anymore..
Andy: grr Ragga Fragga
(The last example is to show "Cheboi" can also be sarcastic.)