View synonyms for uncertain


[ uhn-sur-tn ]


  1. not definitely ascertainable or fixed, as in time of occurrence, number, dimensions, or quality.

    Synonyms: unsure, unpredictable

  2. not confident, assured, or free from hesitancy:

    an uncertain smile.

  3. not clearly or precisely determined; indefinite; unknown:

    a manuscript of uncertain origin.

    Synonyms: undetermined, unsettled

  4. vague; indistinct; not perfectly apprehended:

    an abstruse novel with uncertain themes.

  5. subject to change; variable; capricious; unstable:

    a person of uncertain opinions.

  6. ambiguous; unreliable; undependable:

    Her loyalties are uncertain.

  7. dependent on chance or unpredictable factors; doubtful; of unforeseeable outcome or effect.
  8. unsteady or flickering, as light; of changing intensity or quality.

    Synonyms: irregular


/ ʌnˈsɜːtən /


  1. not able to be accurately known or predicted

    the issue is uncertain

  2. whenpostpositive, often foll by of not sure or confident (about)

    a man of uncertain opinion

  3. not precisely determined, established, or decided

    uncertain plans

  4. not to be depended upon; unreliable

    an uncertain vote

  5. liable to variation; changeable

    the weather is uncertain

  6. in no uncertain terms
    1. unambiguously
    2. forcefully
“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

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Derived Forms

  • unˈcertainly, adverb
  • unˈcertainness, noun
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Other Words From

  • un·certain·ly adverb
  • un·certain·ness noun
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Word History and Origins

Origin of uncertain1

First recorded in 1250–1300; Middle English; un- 1 + certain
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Idioms and Phrases

see in no uncertain terms .
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Synonym Study

Uncertain, insecure, precarious imply a lack of predictability. That which is uncertain is doubtful or problematical; it often involves danger through an inability to predict or to place confidence in the unknown: The time of his arrival is uncertain. That which is insecure is not firm, stable, reliable, or safe, and hence is likely to give way, fail, or be overcome: an insecure foundation, footing, protection. Precarious suggests great susceptibility to failure, or exposure to imminent danger: a precarious means of existence.
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Example Sentences

It’s essential for companies to capitalize on the essential time together during these uncertain times.

Startled and uncertain, Teichner takes in the proposal and answers with a solid maybe.

The end of this sickness is still uncertain and many months away, especially for those who live in the poorest parts of the planet.

Today, the hotel and restaurant remain closed, their future as uncertain as Riley’s.

Back then, it was still uncertain whether fall marathons would be canceled.

If the certainty of the wisdom of uncertainty is itself uncertain, the force of the definition crumbles by logical standards.

In war, he wrote, “everything is uncertain … all military action is intertwined with psychological forces and effects.”

“The jailer had a high-school-age daughter and was uncertain how to help her get in college,” writes Ferris.

Meanwhile, ISIS is on the march, and President Obama strikes an uncertain pose.

Even “destroyed” becomes an uncertain term when applied to these sort of digital files.

Distance, the uncertain light, and imagination, magnified it to a high wall; high as the wall of China.

Uric acid is decreased before an attack of gout and increased afterward, but its etiologic relation is still uncertain.

An estate upon condition is one which depends upon the happening or not happening of some uncertain event.

It is therefore uncertain from these statements which furnace consumes the greater quantity of air.

Again Arabella inclined her head, and looked uneasily round as if uncertain whether to call for assistance.


Definitions and idiom definitions from 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.