Definitions of unstable:

  • adjective:   highly or violently reactive
    Example: "Sensitive and highly unstable compounds"
  • adjective:   disposed to psychological variability
    Example: "His rather unstable religious convictions"
  • adjective:   lacking stability or fixity or firmness
    Example: "Unstable political conditions"
  • adjective:   subject to change; variable
    Example: "Everything was unstable following the coup"
  • adjective:   affording no ease or reassurance
  • adjective:   suffering from severe mental illness