[ fuh-ley-shuh s ]
/ fəˈleɪ ʃəs /


containing a fallacy; logically unsound: fallacious arguments.
deceptive; misleading: fallacious testimony.
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 forms

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for fallacious

British Dictionary definitions for fallacious


/ (fəˈleɪʃəs) /


containing or involving a fallacy; illogical; erroneous
tending to mislead
delusive or disappointinga fallacious hope

Derived Forms

fallaciously, 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