To utter a harsh, flat, croaking sound or cry, as a goose or duck; croak; now, usually, to cry as a duck.To make an outcry: said of persons.n. A harsh, croaking sound.n. The cry of a duck; a quacking.To talk noisily and ostentatiously; make vain and loud pretensions.To play the quack; practise arts of quackery, as a pretender to medical skill.To treat in the manner of a quack; play the quack with.To tamper with dishonestly; use fraudulently.n. An impudent and fraudulent pretender to medical skill; a mountebank; a knavish practitioner of medicine.n. Hence One who pretends to skill or knowledge of any kind which he does not possess; an ignorant and impudent pretender; a charlatan.n. Synonyms Quack, Empiric, Mountebank, Charlatan. A quack is, by derivation, one who talks much without wisdom, and, specifically, talks of his own power to heal; hence, any ignorant pretender to medical knowledge or skill. Empiric is a more elevated term for one who goes by mere experience in the trial of remedies, and is without knowledge of the medical sciences or of the clinical observations and opinions of others; hence, an incompetent, self-confident practitioner. A mountebank is generally a quack, but may be a pretender in any line. Charlatan (literally ‘chatterer’) is primarily applied, not to a person belonging to any particular profession or occupation, but to a pretentious cheat of any sort.Pertaining to or characterized by quackery of any kind; specifically, falsely pretending to cure disease, or ignorantly or fraudulently set forth as remedies: as, a quack doctor; quack medicines.n. See couac.