unreasonable
Americanadjective
-
not reasonable or rational; acting at variance with or contrary to reason; not guided by reason or sound judgment; irrational.
an unreasonable person.
-
not in accordance with practical realities, as attitude or behavior; inappropriate.
His Bohemianism was an unreasonable way of life for one so rich.
- Synonyms:
- nonsensical, stupid, absurd, preposterous, silly, foolish, senseless
-
excessive, immoderate, or exorbitant; unconscionable.
an unreasonable price; unreasonable demands.
- Synonyms:
- extravagant
-
not having the faculty of reason.
adjective
-
immoderate; excessive
unreasonable demands
-
refusing to listen to reason
-
lacking reason or judgment
Other Word Forms
- unreasonableness noun
- unreasonably adverb
Etymology
Origin of unreasonable
First recorded in 1300–50, unreasonable is from the Middle English word unresonabel. See un- 1, reasonable
Explanation
To be unreasonable means acting in an irrational way. Your expectation that your favorite team will win the Super Bowl every year is unreasonable. When someone's unreasonable, they're not using reason, or common sense, to make decisions or demands. Add the prefix un- to reasonable, "having sound judgment," and you get an adjective that's perfect for describing illogical behavior. It's often used for a certain kind of demanding stubbornness too: "It's completely unreasonable to make your server take your soup back five times to warm it up a little more."
Vocabulary lists containing unreasonable
"The Southpaw"
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Chronically Dolores
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Part 3 Vocabulary (Unit 2)
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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.
In 1971, the Supreme Court began to patch this hole in a case called Bivens, approving monetary damages against federal agents who violated the Fourth Amendment’s guarantee against unreasonable search and seizure.
From Slate • Apr. 15, 2026
“That is not unreasonable for a business of this quality,” he said.
From MarketWatch • Apr. 9, 2026
The country's parliament speaker Mohammad Bagher Ghalibaf posted on X that the "workable basis on which to negotiate" had already been violated, making further talks "unreasonable".
From Barron's • Apr. 9, 2026
It’s where I watched Barack Obama get elected twice, the Lakers win back-to-back championships, and where I indulged in countless night caps and an unreasonable amount of all-you-can-eat split pea soup.
From Los Angeles Times • Mar. 26, 2026
“If only” implied “if only we could stay,” and the idea of calling San Francisco home didn’t sound so unreasonable to her.
From "Book Scavenger" by Jennifer Chambliss Bertman
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.
