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.

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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

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Other Word Forms

• unthinkability noun
• unthinkableness noun
• unthinkably adverb

Etymology

Origin of unthinkable

late Middle English word dating back to 1400–50; see origin at un- ¹, thinkable

Example Sentences

These cases are often framed as shocking, unthinkable tragedies—aberrations no one could have predicted.

From Slate • Apr. 25, 2026

“It was almost unthinkable in the 1980s that two men or two women could legally marry under California law,” said Matsumura, the Loyola professor.

From Los Angeles Times • Apr. 25, 2026

Completely free trade makes sense only in a world where disruption is unthinkable.

From The Wall Street Journal • Apr. 15, 2026

For many, the idea of filming and broadcasting such intimate moments, including the actual birth of their child, would be unthinkable.

From BBC • Apr. 4, 2026

But then the unthinkable: “I’ll be there no later than five,” she said.

From "Hope Springs" by Jaime Berry

Related Words

• absurd
• extraordinary
• illogical
• implausible
• impossible
• improbable
• inconceivable
• preposterous
• rare
• unbelievable
• uncommon
• unimaginable
• unlikely
• unreasonable