irrationally

American

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

adverb

in a way that is contrary to reason or is not sensible; illogically.

In firing a highly competent CEO without cause, the Board acted unlawfully, unreasonably, and irrationally.
Stick to your simple calculation and logic, even when markets are behaving irrationally.
in a way that is driven by impulse or instinct rather than reason; without having or being able to use the faculty of reason.

When a reporter started poking around, the suspect began acting irrationally and took off like a wild animal.

Other Word Forms

nonirrationally adverb

Etymology

Origin of irrationally

First recorded in 1640–50; irrational ( def. ) + -ly ( def. )

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.

The most important lesson from that irrationally exuberant time is that overvaluation can lead to below-average returns for years — and even decades.

From MarketWatch • Mar. 13, 2026

I found myself irrationally angry about the way T-Mobile convinced the Backstreet Boys to parody “I Want It That Way” with facile sloganeering.

From Slate • Feb. 8, 2026

But Jacobs also said that “it is incredibly important to be disciplined on price” and that the company won’t “fall irrationally in love with any particular company.”

From Barron's • Jan. 5, 2026

Tom Cross KC, barrister for the two women, told the court that in deciding the clinic should continue to be registered, "the CQC has acted irrationally".

From BBC • Jun. 24, 2025

Humans, I’d noticed, seem to be irrationally fond of dogs, and I could see why a puppy would be easier to cuddle with than, say, a gorilla.

From "The One and Only Ivan" by Katherine Applegate

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023