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unstable

[uhn-stey-buh l] /ʌnˈsteɪ bəl/
adjective
1.
not stable; not firm or firmly fixed; unsteady.
2.
liable to fall or sway.
3.
unsteadfast; inconstant; wavering:
unstable convictions.
4.
marked by emotional instability:
an unstable person.
5.
irregular in movement:
an unstable heartbeat.
6.
Chemistry. noting compounds that readily decompose or change into other compounds.
Origin
1175-1225
1175-1225; Middle English; see un-1, stable2
Related forms
unstableness, noun
unstably, adverb
Synonyms
2. precarious. 2, 3. See unsettled. 3. vacillating.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for unstablest

unstable

/ʌnˈsteɪbəl/
adjective
1.
lacking stability, fixity, or firmness
2.
disposed to temperamental, emotional, or psychological variability
3.
(of a chemical compound) readily decomposing
4.
(physics)
  1. (of an elementary particle) having a very short lifetime
  2. spontaneously decomposing by nuclear decay; radioactive: an unstable nuclide
5.
(electronics) (of an electrical circuit, mechanical body, etc) having a tendency to self-oscillation
Derived Forms
unstableness, noun
unstably, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for unstablest

unstable

adj.

early 13c., "apt to move," from un- (1) "not" + stable (adj.). Cf. Middle High German unstabel. Meaning "liable to fall" is recorded from c.1300; sense of "fickle" is attested from late 13c. An Old English word for this was feallendlic, which might have become *fally.

Online Etymology Dictionary, © 2010 Douglas Harper
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unstablest in Science
unstable
  (ŭn-stā'bəl)   
  1. 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. See more at decay.

  2. Relating to a chemical compound that readily decomposes or changes into other compounds or into elements.

  3. Relating to an atom or chemical element that is likely to share electrons; reactive.

  4. Characterized by uncertain or inadequate response to treatment and the potential for unfavorable outcome, as the status of a medical condition or disease.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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