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

Many players said the game's frame rate - which governs the smoothness of on-screen animations - was unstable.

From BBC

The flooding in Valencia was caused by a Dana phenomenon - when warm, moist air meets cold air, creating an unstable weather system.

From BBC

Antioxidants neutralize free radicals, which are unstable molecules that harm our cells.

From Salon

It’s the story of California — thrilling and a bit unstable at the same time.

From Los Angeles Times

“This is someone who is unstable, obsessed with revenge, consumed with grievance and out for unchecked power.”

From Los Angeles Times

Related Words

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