un·​sta·​ble | \ ˌən-ˈstā-bəl How to pronounce unstable (audio) \

Definition of unstable

: not stable : not firm or fixed : not constant: such as
a : not steady in action or movement : irregular an unstable pulse
b : wavering in purpose or intent : vacillating
c : lacking steadiness : apt to move, sway, or fall an unstable tower
d(1) : liable to change or alteration an unstable economy unstable weather
(2) : readily changing (as by decomposing) in chemical or physical composition or in biological activity
e : characterized by lack of emotional control

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Other Words from unstable

unstableness noun
unstably \ ˌən-​ˈstā-​b(ə-​)lē How to pronounce unstable (audio) \ adverb

Synonyms & Antonyms for unstable



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Choose the Right Synonym for unstable

inconstant, fickle, capricious, mercurial, unstable mean lacking firmness or steadiness (as in purpose or devotion). inconstant implies an incapacity for steadiness and an inherent tendency to change. an inconstant friend fickle suggests unreliability because of perverse changeability and incapacity for steadfastness. performers discover how fickle fans can be capricious suggests motivation by sudden whim or fancy and stresses unpredictability. an utterly capricious critic mercurial implies a rapid changeability in mood. made anxious by her boss's mercurial temperament unstable implies an incapacity for remaining in a fixed position or steady course and applies especially to a lack of emotional balance. too unstable to hold a job

Examples of unstable in a Sentence

an unstable nuclear reactor core the minute we put the books down on the unstable desk, the whole stack went crashing to the floor
Recent Examples on the Web But the pileup around Quinnyon was unstable, officials said. Washington Post, 17 July 2021 Suddenly, the alignment of atoms everywhere is unstable: Clusters of different sizes with arrows pointing either up or down appear all at once, and magnetism is about to be lost. Allison Whitten, Wired, 11 July 2021 Suddenly, the alignment of atoms everywhere is unstable: Clusters of different sizes with arrows pointing either up or down appear all at once, and magnetism is about to be lost. Quanta Magazine, 8 July 2021 Search crews had occasionally faced snags: Efforts had to be called off for 15 hours last week due to concerns over how unstable the debris pile is, and workers were delayed by a smoldering fire in the rubble after the collapse. Nicholas Reimann, Forbes, 6 July 2021 The actress had told The New York Times in a 2018 interview that Tarantino pressured her into operating a car, which she had been warned was unstable. Nick Romano, EW.com, 1 July 2021 Identify or set up reliable testing labs near the sampling sites, since the testing marketplace is currently unstable, rapid turnaround is needed, and many labs do not include assays for public health biomarkers. Aparna Keshaviah, STAT, 27 June 2021 The building was determined to be unstable a year ago, according to a researcher at Florida International University. Editors, USA TODAY, 25 June 2021 Cliff edges are unstable and there are a lot of loose rocks on the top of these high places. Joelle Goldstein, PEOPLE.com, 17 June 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'unstable.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of unstable

13th century, in the meaning defined above

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Time Traveler for unstable

Time Traveler

The first known use of unstable was in the 13th century

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Statistics for unstable

Last Updated

23 Jul 2021

Cite this Entry

“Unstable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unstable. Accessed 27 Jul. 2021.

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More Definitions for unstable



English Language Learners Definition of unstable

: likely to change
: not emotionally or mentally healthy
: not held in a secure position : likely to move or fall


un·​sta·​ble | \ ˌən-ˈstā-bəl How to pronounce unstable (audio) \

Kids Definition of unstable

: not stable an unstable boat


un·​sta·​ble | \ -ˈstā-bəl How to pronounce unstable (audio) \

Medical Definition of unstable

: not stable: as
a : characterized by frequent or unpredictable changes a patient in unstable condition
b : readily changing (as by decomposing) in chemical composition or biological activity unstable compounds
c : characterized by lack of emotional control or stability

More from Merriam-Webster on unstable

Nglish: Translation of unstable for Spanish Speakers


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