unthinkable

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

adjective

inconceivable; unimaginable: the unthinkable size of the universe.
not to be considered; out of the question: Such a suggestion is unthinkable.

noun

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

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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, nounun·think·a·bly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for unthinkable

British Dictionary definitions for unthinkable

unthinkable
/ (ʌnˈθɪŋkəbəl) /

adjective

not to be contemplated; out of the question
unimaginable; inconceivable
unreasonable; improbable

Derived forms of unthinkable

unthinkability or unthinkableness, noununthinkably, 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