1. Lacking stability or fixity or firmness
   "unstable political conditions"; "the tower proved to be unstable in the high wind"; "an unstable world economy" 
2. Highly or violently reactive
   "sensitive and highly unstable compounds" 
3. Affording no ease or reassurance
   - precarious 
4. Suffering from severe mental illness
   - mentally ill, unsound 
5. Disposed to psychological variability
   "his rather unstable religious convictions" 
6. Subject to change; variable
   "everything was unstable following the coup"
   - fluid

Derived forms: unstablest, unstabler

See also: changeable, changeful, coseismal, coseismic, crank, cranky, explosive, impermanent, inconstant, insane, irresolute, reactive, rickety, rocky, seismal, seismic, shaky, temporary, tender, tippy, tipsy, top-heavy, tottering, uneasy, unstableness, unsteady, volatile, volcanic, wobbly, wonky

Antonym: stable

Encyclopedia: Unstable

• Hyperion
• hyperkalemia
• hyperkeratosis
• hyperkeratotic
• hyperkinesis
• hyperkinetic
• hyperkinetic syndrome
• hyperlink
• hyperlipaemia
• hyperlipemia
• hyperlipidaemia
• hyperlipidemia
• hyperlipoidaemia
• hyperlipoidemia
• hyperlipoproteinemia
• hypermarket
• Hypermastigina
• hypermastigote
• hypermedia
• hypermedia system
• hypermenorrhea
• hypermenorrhoea
• hypermetropia
• hypermetropic
• hypermetropy