[fuh-ley-shuh s]
See more synonyms for fallacious on Thesaurus.com
  1. containing a fallacy; logically unsound: fallacious arguments.
  2. deceptive; misleading: fallacious testimony.
  3. disappointing; delusive: a fallacious peace.

Origin of fallacious

First recorded in 1500–10, fallacious is from the Latin word fallāciōsus deceitful, deceptive. See fallacy, -ous
Related formsfal·la·cious·ly, adverbfal·la·cious·ness, nounnon·fal·la·cious, adjectivenon·fal·la·cious·ly, adverbnon·fal·la·cious·ness, nounun·fal·la·cious, adjectiveun·fal·la·cious·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for fallaciousness

Historical Examples of fallaciousness

British Dictionary definitions for fallaciousness


  1. containing or involving a fallacy; illogical; erroneous
  2. tending to mislead
  3. delusive or disappointinga fallacious hope
Derived Formsfallaciously, adverbfallaciousness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for fallaciousness



c.1500, from fallacy (Latin fallacia) + -ous. Related: Fallaciously; fallaciousness.

Online Etymology Dictionary, © 2010 Douglas Harper