simple past tense and past participle of quack

plural of quacking

The sound made by a duck.

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

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

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

present participle of quack

The sound made by a group of ducks; quacks.

Making quacking sounds, or prone to doing so.