Definition of "quack"

Tis hard to say, how much these Arse-wormes do urge us, We now need no Quack but these Jacks for to purge us, [...]

1662, Rump: or an Exact Collection of the Choycest Poems and Songs Relating to Late Times, Vol. II, by ‘the most Eminent Wits’

After ſome Months, the Quack gets privately to Town, [...]

1720, William Derham, Physico-theology

‘if we are ourselves valets, there shall ‘exist no hero for us; we shall not know the hero when we see him;’ - we shall take the quack for a hero; and cry, audibly through all ballot-boxes and machinery whatsoever, Thou art he; be thou King over us!

1843 April, Thomas Carlyle, “ch. 8, The Electon”, in Past and Present, American edition, Boston, Mass.: Charles C[offin] Little and James Brown, published 1843, book II (The Ancient Monk)

The advertising quack who wearies / With tales of countless cures, / His teeth, I've enacted, / Shall all be extracted / By terrified amateurs.

1885, W[illiam] S[chwenck] Gilbert, Arthur Sullivan, composer, “A More Humane Mikado”, in […] The Mikado; or, The Town of Titipu, London: Chappel & Co., […], Act II, page 36

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.

1981, S.O.B. (film)

"I don't want to get into specifics, but when I was born, my parts were considered... ambiguous. The quack of a doctor that delivered me, had trouble assigning a gender. So at his recommendation - and surgical intervention - I was raised as a boy."

2017 March 1, Jocelyn Samara D., Rain (webcomic), Comic 920 - Quack

The very quaik of faſhions, the very hee that / VVeares a Steletto on his chinne.

c. 1635–1636 (date written), Iohn Ford [i.e., John Ford], The Fancies, Chast and Noble: […], London: […] E[lizabeth] P[urslowe] for Henry Seile, […], published 1638, Act III, page 32

[…] it is incredible, and scarce to be imagin’d, how the Posts of Houses, and Corners of Streets were plaster’d over with Doctors Bills, and Papers of ignorant Fellows; quacking and tampering in Physick, and inviting the People to come to them for Remedies;

1722, Daniel Defoe, “A Journal of the Plague Year”, in et al.‎, London: E. Nutt, page 36

Seek out for Plants with SignaturesTo Quack of Universal Cures

1684, Samuel Butler, Hudibras‎, London, Part 3, Canto 1, p. 18

In precisely the same way does a quack doctor prescribe his infallible nostrum to every patient, without taking into account differences of constitution, or [...]

1833, James Rennie, “The Word Gardening”, in Alphabet of Scientific Gardening for the Use of Beginners, London: William Orr, page 2

[R]ecently I examined as many newspapers and magazines as I could lay hands on just to see if I could find in them those old, alluring advertisements, ranging from the quack doctor to the quacker promoter and the quackest oracle of fate. There was nothing doing—everything as clean as a hound's tooth and as wholesome as sunshine.

1916 August 5, Henry D. Estabrook, “Truth in Advertising [advertisement]”, in The Duluth Herald, volume XXXIV, number 102, Duluth, Minn.: The Herald Company, page 6

Finding, perhaps, that there is no solution either in politics or in any existing religion, he [the common man] may cling to the diagnosis of the last and quackest of his doctors: he may believe that art can save himself and the world.

1948, The Prospect before Us: Some Thoughts on the Future, London: Sampson Low, Marston & Co., page 102

When no certain cure exists, quack remedies tend to proliferate and the history of quackery and secret cures is full of extraordinary forms of treatment for the various arthritic disorders.

1976 March 27, F. Dudley Hart, “History of the treatment of rheumatoid arthritis”, in British Medical Journal, volume 1, number 6012, page 763

They desperately want to believe something will help and for that reason they assist one another in obtaining unproven remedies. Such "helpful" promotion is generally more "quack" than fraudulent in nature.

1991, Journal of the Association of Food and Drug Officials, volume 55, York, Pa.: The Association, page 35

[William] Hogarth might have felt some sympathy for [Sally] Mapp as an 'irregular' expert besting pomposity, but this is topped by his sheer relish for her as the Quackest Quack of all, and female to boot. In Hogarth's print the dark goddess rules over her court of fools, men who have taken over the ancient realm of women's healing, and now profit from the people's ills and credulity.

1997, Jenny Uglow, “Allegories of Healing”, in William Hogarth: A Life and a World, London: Faber and Faber, page 506