- (physics, chemistry) Of or pertaining to a physical or chemical state that is relatively long-lived, but may decay to a lower energy state when slightly perturbed or through a quantum transition.
Metastability describes the behaviour of certain physical systems that can exist in long lived states that are less stable than the system's most stable state.
The parameters of excited systems may reach and hold stationary values (a metastable state). But metastable states have finite lifetimes. After a (potentially very long) period of time, spontaneously or under an external action, the characteristic parameters of the state change again to relax to a more stable state.