Definitions by Owen Powers Donovan

quack 

The sound uttered to signify that someone just got scammed or publically shamed.

A guy fails at picking up a girl and walks back to his friends. He is met with a chorus of "Quaaack."

or

"That sucker got seriously quacked by the salesman at GoodGuys. Buyer Protection Program? Quack!"

quack by Owen Powers Donovan July 30, 2003