| metastable | 1. Of uncertain stability; in a condition to pass into another phase when slightly disturbed; e.g., water, when cooled below the freezing point may remain liquid but will at once congeal if a piece of ice is added. 2. Denoting the excited condition of the nucleus of a radionuclide isomer that reaches a lower energy state by the process of isomeric transition decay without changing its atomic number or weight; e.g., 99m99mTc → 9999Tc + g. Origin: meta-+ L. Stabilis, stable (05 Mar 2000) |
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