unstable - definition and synonyms

adjective 

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/ʌnˈsteɪb(ə)l/
  1. 1
    an unstable person becomes angry or upset often and very suddenly

    My father wasn’t a bad man, but he was emotionally unstable.

  2. 3
    an unstable system, situation, or relationship often has serious problems

    an unstable economy

  3. 4
    chemistry an unstable substance reacts very easily with other chemical substances and can be dangerous
  4. 6
    physics an unstable object is likely to move or change because of the forces affecting it