(quacks, quacking, quacked)
1.
If you call someone a quack or a quack doctor, you mean that they claim to be skilled in medicine but are not.
I went everywhere for treatment, tried all sorts of quacks.
N-COUNT: oft N n [disapproval]
2.
Quack remedies or quack cures are medical treatments that you think are unlikely to work because they are not scientific.
ADJ: ADJ n [disapproval]
3.
When a duck quacks, it makes the noise that ducks typically make.
There were ducks quacking on the lawn.
VERB: V
•
Quack is also a noun.
Suddenly he heard a quack.
N-COUNT; SOUND