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.

Macgregor had never known her old friend to be irrational.

From The Wall Street Journal • May 23, 2026

“The current ‘flash-sale wars’ are typical competition under demand-side economies of scale but have escalated into irrational capital burn,” said Chen Tianhao, an associate professor at Tsinghua University.

From Barron's • May 23, 2026

She did some moves that were pretty irrational, and she would have times where she would act on impulse, and it became more and more unstable and unsafe.

From Los Angeles Times • May 13, 2026

A stop loss is an irrational tool deployed to prevent something even more irrational.

From MarketWatch • May 12, 2026

In the back of his head, he knew that his reaction was irrational, unjustified, but...but he couldn’t explain to Koffi the way he felt—unmoored, off-kilter, unsettled.

From "Beasts of Prey" by Ayana Gray

Vocabulary lists containing irrational

Pi Day Vocabulary

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

The Number System

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

Divergent

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!