The characteristic sound made by a duck. noun
The ducks in the pond began to quack loudly.
I could hear the quack of a duck as I walked by the lake.
A person who dishonestly claims to have special knowledge and skill in some field, typically medicine; a charlatan. noun
The man was exposed as a quack after his treatments were found to be ineffective.
She was wary of the quack who promised to cure her illness with unproven methods.
To make the characteristic sound of a duck. verb
The duck quacked as it waddled across the yard.
Every morning, the ducks would quack to greet the sunrise.