How to pronounce quack in English

"To utter a sound like the cry of a duck."

"To make vain and loud pretensions; to boast."

"To act the part of a quack or pretender."

"The cry of the duck or a sound in imitation of it; a hoarse quacking noise."

"A boastful pretender to medical skill; an empiric; an ignorant practitioner."

"Hence one who boastfully pretends to skill or knowledge of any kind not possessed; a charlatan."

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