unthinkable
Americanadjective
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inconceivable; unimaginable.
the unthinkable size of the universe.
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not to be considered; out of the question.
Such a suggestion is unthinkable.
noun
adjective
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not to be contemplated; out of the question
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unimaginable; inconceivable
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unreasonable; improbable
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Etymology
Origin of unthinkable
late Middle English word dating back to 1400–50; see origin at un- 1, thinkable
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.
“It’s allowing us to develop a first reactor within a time frame that had been unthinkable previously,” said Liz Muller, Deep Fission’s chief executive.
From The Wall Street Journal ● Jul. 28, 2026
Anyone who watched the colt win six of eight starts — including the Santa Anita Derby, the Preakness Stakes and finally the Haskell Stakes on July 19, 2025— might find that unthinkable.
From Los Angeles Times ● Jul. 17, 2026
US Supreme Court justices told Congress on Tuesday that escalating threats have forced them to confront dangers once unthinkable for the nation's top judges -- including explaining bulletproof vests to their children.
From Barron's ● Jul. 14, 2026
He appealed directly to the suspect, saying: "Mark, unthinkable harm has been caused to those around you and this has left your relatives and friends utterly devastated. Criminal investigation knows no borders."
From BBC ● Jul. 9, 2026
To treat him with courtesy, on the other hand, was unthinkable.
From "Catch-22" by Joseph Heller
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.
