It will come as no surprise that fallacious is related to the noun fallacy, meaning “delusion” or “falsehood.” Both words come from the Latin word fallacia, which in turn comes from fallere, …

FALLACIOUS definition: containing a fallacy; logically unsound. See examples of fallacious used in a sentence.

To unquestioningly adhere to traditional policies when there is good reason for change can be regarded as a fallacious appeal to authority.

Definition of fallacious adjective in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.

1. Containing or based on a fallacy: a fallacious assumption. 2. Tending to mislead; deceptive: fallacious testimony.

fallacious, adj. meanings, etymology, pronunciation and more in the Oxford English Dictionary

Jan 18, 2026 · Adjective fallacious (comparative more fallacious, superlative most fallacious) Characterized by fallacy; false or mistaken. Synonyms: erroneous, incorrect, wrong; see also …

If an idea, argument, or reason is fallacious, it is wrong because it is based on a fallacy.

What does fallacious mean? Fallacious means misleading, deceptive, or based on false reasoning. "The fallacious advertisement misled customers into buying an ineffective product."

Fallacious definition: Containing or based on a fallacy.