unstable

/ʌnˈsteɪbəl/
adjective
  1. Likely to change or fail; not firmly fixed or steady.
    • The stack of books was unstable and nearly fell over.
    • The political situation in the region remains unstable.
    • After the earthquake, the building's foundation became unstable.
  2. Having or showing a tendency to experience extreme or sudden changes in mood or behavior.
    • His unstable emotions made it hard for him to keep a job.
    • The therapist worked with the patient to manage unstable moods.
    • She has been feeling unstable since the accident.
  3. Tending to decompose or change chemically; not chemically stable.
    • Some radioactive elements are highly unstable.
    • The compound is unstable at room temperature.
    • Chemists must handle unstable substances with great care.