fallacious

adjective

fal·​la·​cious fə-ˈlā-shəs 

1

: embodying a fallacy

a fallacious conclusion

a fallacious argument

2

: tending to deceive or mislead : delusive

false and fallacious hopes

—Conyers Middleton

fallaciously adverb

fallaciousness noun

Did you know?

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 “to deceive.” (Other descendants of fallere in English include fail, false, and fault.) Fallacious arguments are a hot topic among philosophers, and some classic examples include the “ad hominem” fallacy, the “slippery slope” fallacy, and the “red herring” fallacy.

Synonyms

• illegitimate
• illogical
• inconsequent
• inconsequential
• invalid
• irrational
• nonrational
• unreasonable
• unreasoning
• unsound
• weak

Examples of fallacious in a Sentence

it's fallacious to say that something must exist because science hasn't proven its nonexistence

consumers who harbor the fallacious belief that credit-card spending will never catch up with them

Recent Examples on the Web

That will in turn spread on social media, which often plays a disproportional role in boosting these disinformation efforts by providing nearly unlimited platforms for unfiltered content and fallacious and deceptive claims. —Peter Suciu, Forbes, 23 Dec. 2024

But hard evidence in both our nation’s history and our present shows that this reasoning is fallacious. —Ana Raquel Minian, TIME, 30 May 2024

And why not seek the truth, to give order and organization to a chaotic and fallacious narrative and investigative material? —Boris Sollazzo, The Hollywood Reporter, 28 Feb. 2024

This is such a fallacious argument and its presentation as acceptable is abhorrent to our standards of morality. —Letters To The Editor, The Mercury News, 24 Jan. 2024

Word History

First Known Use

15th century, in the meaning defined at sense 1

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Kids Definition

fallacious

adjective

fal·​la·​cious fə-ˈlā-shəs 

1

: containing a fallacy

a fallacious argument

2

: leading in a wrong direction or into a mistaken action or belief

fallaciously adverb

fallaciousness noun