Instability

Characterized by some of the outputs or internal states growing without bounds

In dynamical systems, instability means that some of the outputs or internal states increase with time, without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior. In structural engineering, a structural beam or column can become unstable when excessive compressive load is applied.

From Wikipedia, under CC BY-SA. More on occurri.