In French, au contraire means, literally, on the contrary, and that’s exactly what this loan phrase means in English. It’s often used to mean, roughly, I beg to differ, and it usually creates a humorous or sarcastic tone.
Au contraire is occasionally misspelled oh contraire. But because au contraire is an informal phrase in English, the misspelling is not a huge error.
Hairless is the norm with women? Au contraire, sir. [Salon]
But his insecurities did not hold him back. Au contraire! They propelled him into the spotlight. [Telegraph]
Many people assume that when they reach age 65 and sign up for Medicare, they will be taken care of … Au contraire! Medicare is not free. [Dunwoody Crier]
Did anyone take umbrage at my audaciously superficial questions? Au contraire! The demonstrators were only too happy to talk about their sad rags and their glad rags. [Slate]