Radioactive element, artificially prepared in 1955, atomic no. 100, atomic wt. 257.095; 257Fm has the longest known half-life (100.5 days) of this transuranium element. [E. Fermi, It.-U.S. physicist and Nobel laureate, 1901–1954]
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fer·mi·um 'fer-mē-əm, 'fər- n a radioactive metallic element artificially produced (as by bombardment of plutonium with neutrons) symbol Fm see ELEMENT (table)
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fer·mi·um (Fm) (furґme-əm) [Enrico Fermi, Italian physicist, 1901–1954; winner of the Nobel prize for physics in 1938] the chemical element number 100, atomic weight 253, originally discovered in debris from a thermonuclear explosion in 1952.Medical dictionary. 2011.