unstable

[ uhn-stey-buhl ]

adjective

1. not stable; not firm or firmly fixed; unsteady.
2. liable to fall or sway.

   Synonyms: precarious

3. unsteadfast; inconstant; wavering:

   unstable convictions.

   Synonyms: vacillating

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.

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

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.
2. See more at decay
3. Relating to a chemical compound that readily decomposes or changes into other compounds or into elements.
4. Relating to an atom or chemical element that is likely to share electrons; reactive.
5. Characterized by uncertain or inadequate response to treatment and the potential for unfavorable outcome, as the status of a medical condition or disease.

Derived Forms

• unˈstably, adverb
• unˈstableness, noun

Other Words From

• un·stable·ness noun
• un·stably adverb

Word History and Origins

Origin of unstable¹

First recorded in 1175–1225; Middle English; un- ¹ + stable ²

Synonym Study

See unsettled.

Example Sentences

However, olive oil may not be the best oil to cook with as some people believe it is unstable at high heat.

From Salon

Parts of the landslide have seen recent slowing, and, in some areas, even complete stabilization, the city has reported, but additional rain is always a concern for this unstable region.

From Los Angeles Times

"But ammonium tends to break down under thermal stress. We did some chemistry to convert the unstable ammonium into a more stable amidinium."

From Science Daily

Due to the generally low and unstable productivity of fruits in Borneo's tropical forests compared to Sumatra Island, fruits alone may not be the sole source of food for all four civet species.

From Science Daily

“This can affect the development of atherosclerotic plaques, but also the tendency for the plaques to become unstable and cause a stroke.”

From Science Daily

Related Words

• ambiguous
• changeable
• erratic
• fickle
• insecure
• irrational
• precarious
• risky
• rocky
• sensitive
• shaky
• slippery
• ticklish
• tricky
• uncertain
• unpredictable
• unsettled
• unsteady
• volatile
• weak