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Synonyms

improbable

American  
[im-prob-uh-buhl] / ɪmˈprɒb ə bəl /

adjective

  1. not probable; unlikely to be true or to happen.

    Rain is improbable tonight.
    Synonyms:
    implausible, doubtful, questionable
improbable British  
/ ɪmˈprɒbəbəl /

adjective

  1. not likely or probable; doubtful; unlikely

"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

  • improbability noun
  • improbableness noun
  • improbably adverb
  • superimprobable adjective
  • superimprobableness noun
  • superimprobably adverb

Etymology

Origin of improbable

From the Latin word improbābilis, dating back to 1590–1600. See im- 2, probable

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.

“People underestimate how improbable the improbable is,” says Christian Busch, a University of Southern California business-school professor and the author of “The Serendipity Mindset.”

From The Wall Street Journal • Apr. 4, 2026

“Meme” traders had a hand in the improbable three-year septupling of bitcoin.

From The Wall Street Journal • Apr. 3, 2026

And those were the images that returned with his improbable fifth Masters victory in 2019, fused back and all, achieved at the age of 43.

From BBC • Mar. 28, 2026

At least that’s what one improbable image fantasized in a recent slew of AI-generated “wedding photos” circulating online.

From Los Angeles Times • Mar. 17, 2026

She’d been on her own improbable journey, a victim from a very early age, and she’d learned to fight back— for herself, for others.

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel

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.