Quack v. i. : To utter a sound like the cry of a duck.

Quack v. i. : To make vain and loud pretensions; to boast.

Quack v. i. : To act the part of a quack, or pretender.

Quack n. : The cry of the duck, or a sound in imitation of it; a hoarse, quacking noise.

Quack n. : A boastful pretender to medical skill; an empiric; an ignorant practitioner.

Quack n. : Hence, one who boastfully pretends to skill or knowledge of any kind not possessed; a charlatan.

Quack a. : Pertaining to or characterized by, boasting and pretension; used by quacks; pretending to cure diseases; as, a quack medicine; a quack doctor.

Example:
How does a Quack circumcise a 12 year old boy? How is he helped by his assistants?

Taxonomy
quackery, quack, medicines, treatments, United States, patent medicines, quack medicines, claims, Medical quackery, cures, Radioactive quackery, risks, illness, fraud, accused, effectiveness, bottles, practitioner.

Defination from the web:
quack" derives from the archaic word "quacksalver," of Dutch origin (spelled kwakzalver in contemporary Dutch), meaning "boaster who ...