einsteiniumPronunciation: /ʌɪnˈstʌɪnɪəm/Definition of einsteinium noun [mass noun] the chemical element of atomic number 99, a radioactive metal of the actinide series. Einsteinium does not occur naturally and was discovered in 1953 in debris from the first hydrogen bomb explosion. (Symbol: Es)Origin: 1950s: from the name of Albert Einstein, Albert + -iumeinsteinium in other Oxford dictionaries Definition of einsteinium in the US English dictionary
