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Definition of fallacious

fallacious

/fəˈleɪ.ʃəs/
fal · la · cious
Adverb:fallaciously
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fallacious Lexical Profile

fallacious Game Scores & Validity

• adjective

1

Based on a mistaken belief or unsound reasoning; logically flawed or invalid.

Example

"The debater quickly pointed out that his opponent's conclusion rested on a fallacious assumption."

2

Tending to deceive or mislead; deceptive.

Example

"Consumers were warned to avoid the company's fallacious advertisements promising instant wealth."

Synonyms
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Antonyms
View all antonyms for fallacious

Word Nuance & Usage

'Fallacious' should not be confused with 'falsetto' or 'phallic'; in formal usage, it specifically critiques an argument or belief as resting on flawed logic rather than merely being a deliberate lie.

• Rhymes for fallacious

• Nearby Words

fall
fall creek
fall creek falls
fallacious
fallacy
fallaway
fallback

Word Origin & Etymology

Borrowed in the early 16th century from Late Latin 'fallaciosus', from Latin 'fallacia' (deception, trick), ultimately from 'fallere' (to deceive).

Cite this Entry

Wordmom. (2026). Definition of Fallacious. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/fallacious
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