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

For two years, there was an unstable coexistence of a military-dominated sovereign council and a civilian cabinet.

Read more on BBC

Unlike previous designs that relied on toxic or unstable light absorbers, this new biohybrid model uses non-toxic materials, runs more efficiently, and remains stable without extra additives.

Read more on Science Daily

Here’s the bottom line, according to Martin: If a bubble does burst next year, it won’t be because of valuations but because the market has become “unstable,” as measured by the market’s internals.

Read more on MarketWatch

Conditions such as osteoporosis and arthritis can lead to weakened muscles, fragile bones and unstable joints as well as balance issues.

Read more on Los Angeles Times

Madison especially thought pure direct democracy would prove unstable, a too-slight skiff heaved about in history’s seas.

Read more on The Wall Street Journal

Related Words

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