I. ˈkwak intransitive verb
Etymology: alteration of queck to quack, from Middle English queken, from queke, interjection, of imitative origin
Date: 14th century
: to make the characteristic cry of a duck
II. noun
Date: 1798
: a noise made by quacking
III. intransitive verb
Etymology: quack (IV)
Date: 1628
: to act like a quack
IV. noun
Etymology: short for quacksalver
Date: 1638
1. : charlatan 2
2. : a pretender to medical skill
• quack·ish ˈkwa-kish adjective
V. adjective
Date: 1653
: of, relating to, or used by quacks
quack cancer cures