[ uhn-thing-kuh-buhl ]
See synonyms for: unthinkableunthinkables on Thesaurus.com

  1. inconceivable; unimaginable: the unthinkable size of the universe.

  2. not to be considered; out of the question: Such a suggestion is unthinkable.

  1. something that cannot be conceived or imagined, as something too unusual, vague, or disagreeable: Today's unthinkables are tomorrow's realities.

Origin of unthinkable

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

Other words from unthinkable

  • un·think·a·bil·i·ty, un·think·a·ble·ness, noun
  • un·think·a·bly, adverb

Words Nearby unthinkable

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use unthinkable in a sentence

British Dictionary definitions for unthinkable


/ (ʌnˈθɪŋkəbəl) /

  1. not to be contemplated; out of the question

  2. unimaginable; inconceivable

  1. unreasonable; improbable

Derived forms of unthinkable

  • unthinkability or unthinkableness, noun
  • unthinkably, adverb

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