<p><strong>Adjective:</strong></p><ul><li>Metallurgy: chemically unstable in the absence of certain conditions that would induce stability, but not liable to spontaneous transformation.</li><li>Also pertains to Physics and Chemistry: referring to a body or system existing at an energy level (metastable state) above that of a more stable state, requiring the addition of a small amount of energy to induce a transition to the more stable state.</li></ul>