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

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.

Other Word Forms

• unstableness noun
• unstably 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

America has to attract a constant flow of foreign capital to finance government and imports, an unstable position.

Read more on The Wall Street Journal

The military has since suspended the electoral process and blocked the results' release, and has insisted it thwarted a plot to destabilise the politically unstable country.

Read more on BBC

Over tens of millions of years, this pocket of warm, unstable rock slowly migrated to its current position at a pace of about 20 km per million years.

Read more on Science Daily

Walk around it, and the shifting, light-reflective and -absorbent white forms create an uncanny illusion of the pillar in jumpy, unstable motion.

Read more on Los Angeles Times

But he says that Peru's unstable national governments make change difficult.

Read more on BBC

Related Words

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