To practice or commit quackery (fraudulent medicine). / (obsolete) To make vain and loud pretensions.

To make a noise like a duck. / (intransitive) Of a queen bee: to make a high-pitched sound during certain stages of development.

Falsely presented as having medicinal powers.

(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

The sound made by a duck.

The sound made by a group of ducks; quacks.

present participle of quack

Making quacking sounds, or prone to doing so.

plural of quack

Third-person singular simple present indicative form of quack