quack in Bulgarian

The sound made by a duck.

(pejorative) A fraudulent healer, especially a bombastic peddler in worthless treatments, a doctor who makes false diagnoses for monetary benefit, or an untrained or poorly trained doctor who uses fraudulent credentials to attract patients [from c. 1630]

(figuratively, pejorative) Any similar charlatan or incompetent professional.

To make a noise like a duck.

To practice or commit quackery (fraudulent medicine).