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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
Other Words from unstable Synonyms & Antonyms Choose the Right Synonym Example Sentences Learn More about unstable

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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

 In a hot nail, thermal oscillations make the domains unstable. — Rhett Allain, WIRED, "The Physics of Falling Magnets in Stranger Things Season 3," 9 Aug. 2019 But enthusiasm must be tempered by the fact that black-and-white statistics mask the universal truth that patients experiencing heart failure are inherently unstable. — Paul Sisson, San Diego Union-Tribune, "UCSD heart transplant program posts nation’s best one-year-survival rates," 8 Aug. 2019 Fresh snow can make a layer unstable, and avalanches more likely. — Jenny Howard, National Geographic, "Avalanche safety tips and preparation," 5 Aug. 2019 And this president is that trigger for people who are unstable. — Taylor Kate Brown, SFChronicle.com, "Bay Briefing: Gilroy, El Paso, now Dayton," 5 Aug. 2019 The cliff near Grandview Beach in the Encinitas area is still considered unstable, although clifftop homes are said to be in no immediate danger. — Washington Post, "The Latest: Victims’ relatives had lived in town for years," 4 Aug. 2019 Since the Nigerian economy relies on volatile oil prices alone, an ECOWAS currency could be expected to be highly unstable. — Cheikh Ahmed Bamba Diagne, Quartz Africa, "How Francophone Africa’s France-backed CFA franc works and why it’s controversial," 2 Aug. 2019 Weather conditions can change rapidly, and warming during the day creates more unstable snowpack with a higher risk for avalanches. — National Geographic, "Avalanches, explained," 19 July 2019 Probably that same group again, but on much more unstable footing. — Jon Meoli, baltimoresun.com, "Five questions for the Orioles to answer in the second half of 2019," 12 July 2019

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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More Definitions for unstable

unstable

adjective
How to pronounce unstable (audio)

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

See the full definition for unstable in the English Language Learners Dictionary

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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