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.
But rational investors also know that markets can behave irrationally, and historians have filled books with examples of world leaders who have chosen to irrationally launch or extend wars, even at great economic cost.
From Barron's • May 1, 2026
Needham’s Berg also notes that one pocket of software that has irrationally been swept up in the selloff this week is human-resources and payroll software.
From MarketWatch • Feb. 7, 2026
"The rational world is behaving irrationally by giving him this welcome," she said.
From BBC • Aug. 16, 2025
I can sometimes get irrationally upset by movies with an incredible premise that is poorly executed.
From Salon • Feb. 16, 2025
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
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
