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Synonyms

unthinkable

American  
[uhn-thing-kuh-buhl] / ʌnˈθɪŋ kə bəl /

adjective

  1. inconceivable; unimaginable.

    the unthinkable size of the universe.

  2. not to be considered; out of the question.

    Such a suggestion is unthinkable.

noun

  1. something that cannot be conceived or imagined, as something too unusual, vague, or disagreeable.

    Today's unthinkables are tomorrow's realities.
unthinkable British  
/ ʌnˈθɪŋkəbəl /

adjective

  1. not to be contemplated; out of the question

  2. unimaginable; inconceivable

  3. unreasonable; improbable

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

  • unthinkability noun
  • unthinkableness noun
  • unthinkably adverb

Etymology

Origin of unthinkable

late Middle English word dating back to 1400–50; 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.

"And it is unthinkable - but those thoughts demand to be thought and I will not hide my face. But she needs to come home now."

From BBC • Mar. 25, 2026

It is to ensure that the cost of starting one remains permanently unthinkable.

From The Wall Street Journal • Mar. 24, 2026

Read: It was unthinkable a couple of weeks ago, but could the next move by the Fed be a rate hike?

From MarketWatch • Mar. 18, 2026

Also read: It was unthinkable a couple of weeks ago, but could the next move by the Fed be a rate hike?

From MarketWatch • Mar. 16, 2026

Just before the voyage, in January 1941, the unthinkable happened.

From "The Woman All Spies Fear" by Amy Butler Greenfield

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.