noun
The sound made by a duck.
verb
To make a noise like a duck.
(intransitive) Of a queen bee: to make a high-pitched sound during certain stages of development.
interjection
A duck's quack.
noun
(derogatory) 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
(figuratively, derogatory) Any similar charlatan or incompetent professional.
(humorous slang, mildly derogatory) Any doctor.
verb
To practice or commit quackery (fraudulent medicine).
(obsolete) To make vain and loud pretensions.
adjective
Falsely presented as having medicinal powers.