the harsh, throaty cry of a duck or any similar sound.

verb (used without object)

to utter the cry of a duck or a sound resembling it.

Origin of quack

1610–20; imitative; compare Dutch kwakken, German quacken




a fraudulent or ignorant pretender to medical skill.
a person who pretends, professionally or publicly, to skill, knowledge, or qualifications he or she does not possess; a charlatan.


being a quack: a quack psychologist who complicates everyone's problems.
presented falsely as having curative powers: quack medicine.
of, relating to, or befitting a quack or quackery: quack methods.

verb (used with object)

to treat in the manner of a quack.
to advertise or sell with fraudulent claims.

Origin of quack

First recorded in 1620–30; short for quacksalver
Related formsquack·ish, adjectivequack·ish·ly, adverbquack·ish·ness, noun

Synonyms for quack

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for quack



verb (intr)

(of a duck) to utter a harsh guttural sound
to make a noise like a duck


the harsh guttural sound made by a duck

Word Origin for quack

C17: of imitative origin; related to Dutch kwakken, German quacken




  1. an unqualified person who claims medical knowledge or other skills
  2. (as modifier)a quack doctor
British, Australian and NZ informal a doctor; physician or surgeon


(intr) to act in the manner of a quack
Derived Formsquackish, adjective

Word Origin for quack

C17: short for quacksalver
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for quack

"to make a duck sound," 1610s, earlier quake (1520s), variant of quelke (early 14c.), of echoic origin (cf. Middle Dutch quacken, Old Church Slavonic kvakati, Latin coaxare "to croak," Greek koax "the croaking of frogs," Hittite akuwakuwash "frog"). Middle English on the quakke (14c.) meant "hoarse, croaking." Related: Quacked; quacking.


"medical charlatan," 1630s, short for quacksalver (1570s), from obsolete Dutch quacksalver (modern kwakzalver), literally "hawker of salve," from Middle Dutch quacken "to brag, boast," literally "to croak" (see quack (v.)) + salf "salve," salven "to rub with ointment" (see salve (v.)). As an adjective from 1650s. The oldest attested form of the word in this sense in English is as a verb, "to play the quack" (1620s). The Dutch word also is the source of German Quacksalber, Danish kvaksalver, Swedish kvacksalvare.


duck sound, 1839, from quack (v.).

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for quack




An untrained person who pretends to be a physician and dispenses medical advice and treatment.
A charlatan.
Related formsquacker•y n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.