Quack

Part of speech: noun (n.)

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

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

3. Hence, one who boastfully pretends to skill or knowledge of any kind not possessed; a charlatan. Quacks political; quacks scientific, academical. Carlyle.

Part of speech: verb (v.)

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

2. To make vain and loud pretensions; to boast. " To quack of universal cures." Hudibras.

3. To act the part of a quack, or pretender.

Part of speech: adjective (a.)

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