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.

However, she said she had experienced fear and irrational guilt after Eliza's diagnosis.

From BBC • Mar. 22, 2026

While the motives that drive a knight are often human, political, or both, the logic is as miraculous and irrational as a muddy hedge knight crawling out from under a fallen dragon.

From Salon • Feb. 25, 2026

Freight was another sector that some analysts said was subjected to irrational AI fears last week.

From MarketWatch • Feb. 17, 2026

The stock market behaves a lot like a toddler: a short attention span, active imagination and some irrational fears.

From The Wall Street Journal • Jan. 29, 2026

To have positive liberty, he explained, is to take control of one’s own mind; to be liberated from irrational fears and beliefs, from addictions, superstitions and all other forms of self-coercion.

From "Educated" by Tara Westover

Vocabulary lists containing irrational

Pi Day Vocabulary

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The Number System

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