Metastable equilibrium refers to a state in which a system is stable under small disturbances but can transition to a more stable state if sufficiently perturbed. In this state, the system appears to be in balance, yet it is not in the lowest energy configuration. This concept is often observed in physical and chemical systems, such as in certain types of crystals or chemical reactions. An example of metastable equilibrium is a supercooled liquid, which remains liquid below its freezing point. It can exist in this state for a long time but will eventually crystallize if disturbed. Understanding metastable equilibrium is important in fields like thermodynamics and materials science.