Green’s Dictionary of Slang

an excl. spoken as a challenge, say that again!

1922		Joyce Ulysses 306: I called about the poor and water rate, Mr Boylan. You what? The water rate, Mr Boylan. You whatwhat?
1959		W. Hall Long and the Short and the Tall Act I: You what! What do you think you’re on? You’re father’s yacht?
1962		A. Wesker Chips with Everything I v: andrew: I’ve just straightened it, Serg – or Flight – or Flight Sergeant. flight sergeant: You what?
1978		P. Theroux Picture Palace 237: No matter how Phoebe tried to defend herself Papa would stoop and say, You what?
1986		F. Taylor Auf Wiedersehen Pet Two 223: They stared at him blankly. ‘You what?’ said Moxey.