irrationally
Americanadverb
-
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
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.
People can act irrationally, change their habits, seek therapy, strengthen their commitment, or grow in ways that a mathematical model cannot fully anticipate.
From Science Daily ● Sep. 7, 2026
But it can also result in “fire sale” prices when the market value falls irrationally below underlying fundamentals.
From Barron's ● Mar. 13, 2026
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
He disliked Mordred irrationally, as a dog dislikes a cat—and he felt ashamed of the dislike, because it was a confused principle of his to help the younger Knights.
From "The Once and Future King" by T. H. White
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
