Definition of "quack" []

• The characteristic sound uttered by a duck. (noun)
• To utter the characteristic sound of a duck. (verb-intransitive)
• An untrained person who pretends to be a physician and dispenses medical advice and treatment. (noun)
• A charlatan; a mountebank. (noun)
• Relating to or characteristic of a quack: a quack cure. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The term quack actually comes from the word quicksilver and refers to the so called early drug doctors and piss prophets refers to those who drew the astrological figure or a sick person, his urine being brought to the physician at that moment in time to represent part of his body."
• "Hence the term quack-salver was commonly used in the seventeenth century, signifying an ignorant person, who was wont to extol the curative virtues of his salves."
• "Just as you go back to the basics when problems crop up with your duck dog, the quack is your initial point of reference with your call."