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 …

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

The most common fallacious argument is that current climate change must be natural because climate has changed naturally in the past.

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

Sep 10, 2025 · There is a widely diffused notion that among all specimens of animal creation man alone possesses any glimmering of reason. This notion is largely fallacious. It is one of those ideas, based …

There are five meanings listed in OED's entry for the adjective fallacious, one of which is labelled obsolete. See ‘Meaning & use’ for definitions, usage, and quotation evidence.

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.

Definition of fallacious. English dictionary and integrated thesaurus for learners, writers, teachers, and students with advanced, intermediate, and beginner levels.

A fallacy is the use of invalid or otherwise faulty reasoning in the construction of an argument [1][2] that may appear to be well-reasoned if unnoticed. The term was introduced in the Western intellectual …