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.
And he wanted to show that the state Supreme Court’s ruling that Pitchford’s lawyer had waived relief was not merely debatable but unreasonable even by the AEDPA’s demanding standards.
From Slate • Apr. 10, 2026
“That is not unreasonable for a business of this quality,” he said.
From MarketWatch • Apr. 9, 2026
It isn’t unreasonable to expect returns of over 50% by the end of this year.
From Barron's • Mar. 19, 2026
Airlines and their trade association argue that the Biden administration’s wheelchair regulations exceed the Department of Transportation’s statutory authority and violate the Administrative Procedure Act, claiming the requirements impose unreasonable burdens on air carriers.
From Los Angeles Times • Mar. 15, 2026
He decided not to tell anyone what he was planning, on the not entirely unreasonable basis that they would have told him not to do it.
From "The Graveyard Book" by Neil Gaiman
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.
