Translation guide
The sound a duck makes, or a person pretending to be a doctor.
The noise a duck makes.
A person who pretends to be a doctor without qualifications.
Literally 'fake doctor'. The standard term for a quack doctor.
He was exposed as a quack.
A colloquial term for an incompetent or quack doctor. Often used humorously.
That doctor is a quack.
Literally 'underground doctor', implying unlicensed practice.
It's dangerous to have surgery by a quack.