- 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 unstable on Thesaurus.com
2. precarious. 2, 3. See unsettled. 3. vacillating.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- 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
Word Origin and History for unstably
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.