What is the meaning of unstable?

adjective

• Lacking stability or fixity or firmness.
  • usage: "unstable political conditions"; "the tower proved to be unstable in the high wind"; "an unstable world economy"
• Highly or violently reactive.
  • usage: "sensitive and highly unstable compounds"
• Affording no ease or reassurance.
  • usage: "a precarious truce"
  • synonyms: precarious
• Suffering from severe mental illness.
  • usage: "of unsound mind"
  • synonyms: mentally ill, unsound
• Disposed to psychological variability.
  • usage: "his rather unstable religious convictions"
• Subject to change; variable.
  • usage: "a fluid situation fraught with uncertainty"; "everything was unstable following the coup"
  • synonyms: fluid