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, meaning …

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

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

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

Fallacious comes ultimately from the Latin fallax, "deceptive." The word fallacious might describe an intentional deception or a false conclusion coming from bad science or incomplete understanding.

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

Feb 21, 2026 · Adjective fallacious (comparative more fallacious, superlative most fallacious) Characterized by fallacy; false or mistaken. Synonyms: erroneous, incorrect, wrong; see also …

Fallacious definition: Containing or based on a fallacy.

Fallacious comes ultimately from the Latin fallax, "deceptive." The word fallacious might describe an intentional deception or a false conclusion coming from bad science or incomplete understanding.