metastability 

https://doi.org/10.1351/goldbook.M03871
A term that describes the state of a phase in which an energy barrier considerably higher than k T must be surmounted before this phase can transform to a phase of lower molar Gibbs energy and molar Helmholtz energy, where k is the Boltzmann constant and T the thermodynamic temperature.
Note:
In a thermodynamic sense, the equilibrium state is the state with the lowest molar Gibbs energy; a metastable state corresponds to a relative minimum in the molar Gibbs energy.
Source:
PAC, 1994, 66, 577. (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 586 [Terms] [Paper]
Citation: 'metastability' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.M03871 RIS BibTex EndNote
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Last revised: February 24, 2014