Definition of "quack" in English

noun

1. The sound made by a duck.

   • Did you hear that duck make a quack?

verb

1. To make a noise like a duck.

   • The more breadcrumbs I threw on the ground, the more they quacked.
   • Do you hear the ducks quack?

2. (intransitive) Of a queen bee: to make a high-pitched sound during certain stages of development.

interjection

1. A duck's quack.

noun

1. (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

   • That doctor is nothing but a lousy quack!
   • 1662, Rump: or an Exact Collection of the Choycest Poems and Songs Relating to Late Times, Vol. II, by ‘the most Eminent Wits’ Tis hard to say, how much these Arse-wormes do urge us, We now need no Quack but these Jacks for to purge us, …
   • Polly (to security guard, referring to Dr. Feingarten): Are you going to let that shyster in there? Dr. Feingarten: I could sue you, Polly. A shyster is a disreputable lawyer. I'm a quack.

2. (figuratively, derogatory) Any similar charlatan or incompetent professional.

3. (humorous slang, mildly derogatory) Any doctor.

   • That quack wants me to quit smoking, eat less, and start exercising. The nerve!

verb

1. To practice or commit quackery (fraudulent medicine).

2. (obsolete) To make vain and loud pretensions.

adjective

1. Falsely presented as having medicinal powers.

   • Don't get your hopes up; that's quack medicine!