- not stable; not firm or firmly fixed; unsteady.
- liable to fall or sway.
- unsteadfast; inconstant; wavering: unstable convictions.
- marked by emotional instability: an unstable person.
- irregular in movement: an unstable heartbeat.
- Chemistry. noting compounds that readily decompose or change into other compounds.
Origin of unstable
SynonymsSee more synonyms for on Thesaurus.com
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Related Wordstricky, ambiguous, uncertain, irrational, sensitive, unsettled, insecure, shaky, weak, precarious, rocky, unpredictable, fickle, volatile, wobbly, ticklish, slippery, changeable, unsteady, erratic
Examples from the Web for unstable
You lethargic, unfocused, unstable, lazy, hazy, crazy time of year.Our Doomed Love Affair with Summer
P. J. O’Rourke
August 30, 2014
The initial result was negative, but much of the area was still on fire and too unstable to search.My Building Exploded. I Survived: Harlem Miracle Man Tells His Story
March 13, 2014
Erica is the foil to the unstable, decaying Beth—a kind, virtuous, smooth-skinned girl next door.Anna Kendrick: Queen Bee of the 2014 Sundance Film Festival
January 23, 2014
The value may be unstable, but it has trended mainly up and to the right, with crashes followed by climbs past the previous high.Should Baby Boomers Invest in Bitcoin?
January 9, 2014
We know that Dana is unstable, just based on her having tried to kill herself.‘Homeland’ Star Morgan Saylor: TV’s Most Hated Character Talks Back
October 7, 2013
All his weight was on one foot, and he was in a state of unstable equilibrium.White Fang
Yes, indeed, yes; I know she's as unstable as water and as hard to hold as a puff of wind.The Christian
Moral standards are as unstable as the shifting sands of the sea.Sex=The Unknown Quantity
We can see here very clearly how unstable a thing polytheism is.History of Religion
They are unstable, improvident, easily discouraged, easily led astray.Impressions of South Africa
- lacking stability, fixity, or firmness
- disposed to temperamental, emotional, or psychological variability
- (of a chemical compound) readily decomposing
- (of an elementary particle) having a very short lifetime
- spontaneously decomposing by nuclear decay; radioactivean unstable nuclide
- electronics (of an electrical circuit, mechanical body, etc) having a tendency to self-oscillation
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
Word Origin and History for unstable
Online Etymology Dictionary, © 2010 Douglas Harper
- 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.
- Relating to a chemical compound that readily decomposes or changes into other compounds or into elements.
- Relating to an atom or chemical element that is likely to share electrons; reactive.
- 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.