a radioactive, metallic chemical element, one of the actinides, discovered in the debris of the first thermonuclear explosion in 1952, but now produced by bombarding plutonium with neutrons: symbol, Es; at. no., 99
See einsteinium in American Heritage Dictionary 4
(īn-stīˈnē-əm)
noun Symbol Es
A synthetic transuranic element first produced by neutron irradiation of uranium in a thermonuclear explosion and now usually produced in the laboratory by irradiating plutonium and other elements. Its longest-lived isotope is Es 254 with a half-life of 276 days. Atomic number 99; melting point 860°C. See Table at element.