Adjective unstable has 6 senses
  1. unstable - lacking stability or fixity or firmness; "unstable political conditions"; "the tower proved to be unstable in the high wind"; "an unstable world economy"
    stable, firm, steady, unfluctuating, lasting, stabile, stabilized, stabilised
  2. unstable - highly or violently reactive; "sensitive and highly unstable compounds"
    unreactive (indirect, via reactive)
  3. precarious, unstable - affording no ease or reassurance; "a precarious truce"
    Antonyms: easy, at ease (indirect, via uneasy)
  4. mentally ill, unsound, unstable - suffering from severe mental illness; "of unsound mind"
    Antonym: sane (indirect, via insane)
  5. unstable - disposed to psychological variability; "his rather unstable religious convictions"
    resolute (indirect, via irresolute)
  6. fluid, unstable - subject to change; variable; "a fluid situation fraught with uncertainty"; "everything was unstable following the coup"
    Antonym: unchangeable (indirect, via changeable)