unstable

adjective
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 unstably (audio) \ adverb

Synonyms & Antonyms for unstable

Synonyms

unbalanced, unsteady

Antonyms

balanced, equilibrated, stabilized, stable, steady

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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

The results suggest that Kenya’s ancient herders constructed them as a communal effort to cope with an unstable environment and a shifting cultural frontier. Kiona N. Smith, Ars Technica, "Archaeologists explore East Africa’s ancient monumental cemeteries," 21 Aug. 2018 Residents are concerned that the iceberg is unstable and could roll over or break apart at any time. Avery Thompson, Popular Mechanics, "Giant Iceberg Threatens Entire Greenland Village," 19 July 2018 Neither Joachim Löw, the Germany manager, nor Arsène Wenger, until recently of Arsenal, would likely enjoy the inherently unstable environment Pérez has created. Rory Smith, New York Times, "Zinedine Zidane Leaves Florentino Pérez’s Real Madrid on His Own Terms," 31 May 2018 Inconsistency and an unstable environment and constant coaching changes really set McLemore back. Jason Jones, sacbee, "From Cousins to Papagiannis, the good and bad of the Kings' lottery picks since 2007 | The Sacramento Bee," 14 May 2018 If the star was unstable and blasted off a lot of its outer layers before exploding, then the material ejected by the supernova will slam into it and create an extremely bright event. John Timmer, Ars Technica, "Atoms may come apart as the Universe’s biggest stars explode," 24 Oct. 2018 The temperature difference makes the air unstable, because hot air rises and cooler air sinks. Angela Fritz, Washington Post, "Watch this monster dust devil follow a guy down the road in Arizona," 31 May 2018 By ending the individual mandate, by allowing for more bare-bones insurance policies, and by narrowing the time window to apply for Obamacare policies, Trump has rendered the ACA unstable and unaffordable. Andrew Sullivan, Daily Intelligencer, "Obama’s Legacy Has Already Been Destroyed," 18 May 2018 Nuclear explosions release enormous amounts of heat and energy, and the North’s largest test in September was believed early on to have rendered the site in northeastern North Korea unstable. Christopher Bodeen, USA TODAY, "Chinese geologists say North Korea nuclear test site collapsed, may explain end of program," 25 Apr. 2018

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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Statistics for unstable

Last Updated

14 May 2019

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Time Traveler for unstable

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

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More Definitions for unstable

unstable

adjective

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

unstable

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

Kids Definition of unstable

: not stable an unstable boat

unstable

adjective
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

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More from Merriam-Webster on unstable

Rhyming Dictionary: Words that rhyme with unstable

Thesaurus: All synonyms and antonyms for unstable

Spanish Central: Translation of unstable

Nglish: Translation of unstable for Spanish Speakers

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