Definitions

irrational

[ih-rash-uh-nl, -rash-nl] / ɪˈræʃ ə nl, -ˈræʃ nl /

ADJECTIVE

illogical, senseless

Synonyms

STRONGEST

aberrant absurd crazy foolish incoherent insane preposterous ridiculous stupid unreasonable unsound unwise wrong

STRONG

invalid loony raving silly wild

WEAK

brainless cockamamie delirious demented disconnected disjointed distraught fallacious flaky freaky injudicious kooky mad mindless nonsensical nutty off-the-wall reasonless sophistic specious unreasoning unstable unthinking wacky

Antonyms

STRONGEST

balanced logical rational realistic reasonable responsible sane sensible serious smart sound thoughtful well wise

WEAK

reflective stable

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Detective Peter Doomanis of the Los Angeles Police Department said in his declaration, filed with Carpenter's petition, that he believes the man has "developed a disturbing and irrational fixation on petitioner".

From BBC • Jun. 2, 2026

Reading a review … it’s something rational that is describing something irrational.

From Los Angeles Times • May 26, 2026

Macgregor had never known her old friend to be irrational.

From The Wall Street Journal • May 23, 2026

“I think that irrational exuberance that we saw in the dot com era … is just window dressing to cloak what, to me, is normalizing an addictive behavior in our society,” he said.

From MarketWatch • May 19, 2026

I have no wish to put myself in the same category: irrational, petulant.

From "Cat's Eye" by Margaret Atwood

Vocabulary lists containing irrational

Pi Day Vocabulary

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The Number System

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Divergent

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