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

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 These are critical times for unstable programs in this meat-grinder of a league. Joseph Goodman | Jgoodman@al.com, al, 17 Sep. 2022 The researchers posit that an 83rd moon became unstable, and its orbit swung too close to Saturn. Joshua Hawkins, BGR, 16 Sep. 2022 This instability and the rise in power of Adolf Hitler, in an economically and politically unstable Germany, led to the start of another war in Europe. Caitlin Mclean, USA TODAY, 16 Sep. 2022 Then there is the mercurial and increasingly unstable balance of geopolitics driving millions from their homes and into refugee camps and migrant housing, which are fertile grounds for infectious diseases to spread. Time, 15 Sep. 2022 Housing advocates, however, say this approach runs counter to the intent of the voucher program by pushing the poorest residents into unstable neighborhoods with few social services or amenities. Giacomo Bologna, Washington Post, 14 Sep. 2022 That's considered an unstable way of operating a nuclear plant, which could lead to damage to key equipment including turbines and pumps. Karl Ritter, ajc, 11 Sep. 2022 That’s considered an unstable way of operating a nuclear plant, which could lead to damage to key equipment including turbines and pumps. Karl Ritter, Chicago Tribune, 11 Sep. 2022 But burdensome taxes and high costs of entry have created a crisis within the increasingly unstable market, which has been flooded in recent years by illicit growers and dealers selling their cannabis at cheaper prices. Mitch Koss, NBC News, 8 Sep. 2022 See More

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.

First Known Use of unstable

13th century, in the meaning defined above

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Time Traveler for unstable

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

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Dictionary Entries Near unstable



unstable angina

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Last Updated

21 Sep 2022

Cite this Entry

“Unstable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unstable. Accessed 24 Sep. 2022.

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More Definitions for unstable


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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