from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Lying; untruthful: a mendacious child.
  • adj. False; untrue: a mendacious statement. See Synonyms at dishonest.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. lying, untruthful or dishonest
  • adj. false or untrue

from the GNU version of the Collaborative International Dictionary of English

  • adj. Given to deception or falsehood; lying.
  • adj. False; counterfeit; containing falsehood.

from The Century Dictionary and Cyclopedia

  • Given to lying; speaking falsely; falsifying.
  • Having the character of a lie; false; untrue: as, a mendacious report; mendacious legends.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. intentionally untrue
  • adj. given to lying


From Latin mendācium, lie, from mendāx, mendāc-, mendacious.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Middle French mendacieux, from Latin mendācium ("lie, untruth"), from mendāx ("lying"). (Wiktionary)



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  • Loved this word ever since Big Daddy in Cat on a Hot Tin Roof said mendacity with such deliciousness!

    September 6, 2012

  • Bernstein said:

    "In the case George W. Bush, the American system has obviously failed -- tragically -- about which we can talk more in a minute. But imagine the difference in our worldview today, had the institutions -- particularly of government -- done their job to insure that a mendacious and dangerous president (as has since been proven many times over, beyond mere assertion) be restrained in a war that has killed thousands of American soldiers, brought turmoil to the lives of millions, and constrained the goodwill towards the United States in much of the world."

    January 25, 2007