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.

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

On its own, a stop loss is technically irrational.

From MarketWatch • May 12, 2026

John says at first the changes were attributed to the menopause, but in March 2023 he noticed his wife had become more irrational and did not react as expected when she had a car crash.

From BBC • May 6, 2026

However, irrational numbers, unlike zero, could not easily be ignored by the Greeks.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

Vocabulary lists containing irrational

Pi Day Vocabulary

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The Number System

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Divergent

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