unstable
Americanadjective
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not stable; not firm or firmly fixed; unsteady.
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liable to fall or sway.
- Synonyms:
- precarious
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unsteadfast; inconstant; wavering.
unstable convictions.
- Synonyms:
- vacillating
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marked by emotional instability.
an unstable person.
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irregular in movement.
an unstable heartbeat.
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Chemistry. noting compounds that readily decompose or change into other compounds.
adjective
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lacking stability, fixity, or firmness
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disposed to temperamental, emotional, or psychological variability
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(of a chemical compound) readily decomposing
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physics
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(of an elementary particle) having a very short lifetime
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spontaneously decomposing by nuclear decay; radioactive
an unstable nuclide
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electronics (of an electrical circuit, mechanical body, etc) having a tendency to self-oscillation
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Liable to undergo spontaneous decay into some other form. For example, the nucleus of uranium 238 atom is unstable and changes by radioactive decay into the nucleus of thorium 234, a lighter element. Many subatomic particles, such as muons and neutrons, are unstable and decay quickly into other particles.
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See more at decay
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Relating to a chemical compound that readily decomposes or changes into other compounds or into elements.
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Relating to an atom or chemical element that is likely to share electrons; reactive.
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Characterized by uncertain or inadequate response to treatment and the potential for unfavorable outcome, as the status of a medical condition or disease.
Related Words
See unsettled.
Other Word Forms
- unstableness noun
- unstably adverb
Etymology
Origin of unstable
First recorded in 1175–1225; Middle English; un- 1 + stable 2
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
America has to attract a constant flow of foreign capital to finance government and imports, an unstable position.
The military has since suspended the electoral process and blocked the results' release, and has insisted it thwarted a plot to destabilise the politically unstable country.
From BBC
Over tens of millions of years, this pocket of warm, unstable rock slowly migrated to its current position at a pace of about 20 km per million years.
From Science Daily
Walk around it, and the shifting, light-reflective and -absorbent white forms create an uncanny illusion of the pillar in jumpy, unstable motion.
From Los Angeles Times
But he says that Peru's unstable national governments make change difficult.
From BBC
Definitions and idiom definitions from Dictionary.com 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.
