Definitions
1.NounThe vocalisation made by a duck."Did you hear that duck make a quack?"
2.VerbOf a duck, to make its characteristic vocalisation."The more breadcrumbs I threw on the ground, the more they quacked.; Do you hear the ducks quack?"
3.VerbTo make a sound similar to the quack of a duck.
4.VerbOf a queen bee: to make a high-pitched sound during certain stages of development.
5.InterjectionA duck's quack.
6.NounA 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 .mw-parser-output .defdate{font-size:smaller}"That doctor is nothing but a lousy quack!"
7.NounAny similar charlatan or incompetent professional.
8.NounAny doctor."That quack wants me to quit smoking, eat less, and start exercising. The nerve!"
9.VerbTo practice or commit quackery (fraudulent medicine).
10.VerbTo make vain and loud pretensions.
11.AdjectiveFalsely presented as having medicinal powers."Don't get your hopes up; that's quack medicine!"