quack

(noun) an untrained person who pretends to be a physician and who dispenses medical advice.

(noun) the harsh sound of a duck.

(verb) utter quacking noises. Examples: "The ducks quacked."

(verb) act as a medical quack or a charlatan.

(adj) medically unqualified. Synonyms: quack(prenominal). Examples: "A quack doctor."