quack

n. one who practices medicine without having the proper qualifications; impostor, charlatan; sound made by a duck

adj. impersonating, posing; involved in deceit

v. produce a quacking sound like that of a duck; impersonate, pose as a professional (esp. a doctor); deceive, mislead

Quack can refer to:the noise made by several species of ducka person who practices quackery, i.e., an impostor who claims to have qualifications to practice medicinecouch-grass or quack-grass, Elymus repens, synonyms: Agropyron repens, Triticum repensQuack (comics), an independent-comics series published by Star Reach in the 1970s.A Quack can also be a derogatory term for a Hypnotist, Astrologer or Therapist. This term was popularized in the 1949 Movie Whirlpool, in which the protagonist falls victim to a Quack Hypnotist.
See more at Wikipedia.org...

(v. i.)
To utter a sound like the cry of a duck.
  

(v. i.)
To make vain and loud pretensions; to boast.
  

(v. i.)
To act the part of a quack, or pretender.
  

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

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

(n.)
A boastful pretender to medical skill; an empiric; an ignorant practitioner.
  

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

Any person with characteristic pretensions, misrepresentations, practices, and/or methods who is unqualified or incompetent in the field to which such distinctions pertain. The word “quack” traces to two Dutch words: the obsolete verb “quacken,” which meant “to chatter or prattle,” and “salf,” a relative of the English word “salve.” Old-time quacksalvers were simply persons who bragged about the medicinals they offered.

Noun
1. an untrained person who pretends to be a physician and who dispenses medical advice
(hypernym) doctor, doc, physician, MD, Dr., medico
2. the harsh sound of a duck
(hypernym) sound
Verb
1. utter quacking noises; "The ducks quacked"
(hypernym) utter, emit, let out, let loose
2. act as a medical quack or a charlatan
(hypernym) act, behave, do
(classification) medicine, practice of medicine
Adjective
1. medically unqualified; "a quack doctor"
(synonym) quack(a)
(similar) unqualified