From wiktionary[0]:

> chapeau (interjection) - well done, a verbal representation of a hat tip

Don't go to wikipedia[1], or else you'll be confused by "A chapeau is a flat-topped hat once worn by senior clerics."

Thanks for the new word, justinator!

[0] https://en.wiktionary.org/wiki/chapeau

[1] https://en.wikipedia.org/wiki/Chapeau