metastable states

Metastable states are conditions that appear stable but can shift to a more stable state if disturbed.

A ball resting in a shallow depression on a hillside is metastable—it stays put until nudged, then rolls to the valley floor.

The term applies across physics, chemistry, and materials science: The supercooled water remained in a metastable state until a seed crystal triggered freezing.

Metastable states persist because they lack the energy to overcome the barrier to true stability.