unthinkable

adjective

un·​think·​able ˌən-ˈthiŋ-kə-bəl 

1

: not capable of being grasped by the mind

2

: being contrary to what is reasonable, desirable, or probable : being out of the question

unthinkability

ˌən-ˌthiŋ-kə-ˈbi-lə-tē 

noun

unthinkably

ˌən-ˈthiŋ-kə-blē 

adverb

Synonyms

• incredible
• incredulous
• unlikely
• impossible
• inconceivable
• unimaginable
• fantastical
• unbelievable

Examples of unthinkable in a Sentence

to most people it seemed unthinkable that such a gentle man could be guilty of such awful crimes

Recent Examples on the Web

Only a few years ago, with many NATO members struggling, or not even bothering to struggle, to reach an earlier target of 2 percent, such a commitment would have been unthinkable. —The Editors, National Review, 27 June 2025

Before Russia’s full-scale invasion of Ukraine, such a strike would have been unthinkable. —Florence Gaub, Foreign Affairs, 24 June 2025

That immediately set in the previously unthinkable question of whether the Cavs could afford to keep him given their second-apron situation. —John Hollinger, New York Times, 17 June 2025

The online activity level and the engagement of people with news and blogs, and online material are just unthinkable. —Georg Szalai, HollywoodReporter, 16 June 2025

Word History

First Known Use

15th century, in the meaning defined at sense 1

Phrases Containing unthinkable

• the unthinkable

Rhymes for unthinkable

• thinkable

Kids Definition

unthinkable

adjective

un·​think·​able ˌən-ˈthiŋ-kə-bəl 

ˈən-

: not to be thought of or considered as possible

unthinkable cruelty