Source : Webster's Revised Unabridged Dictionary (1913)

Uranium \U*ra"ni*um\, n. [NL., from Uranus the planet. See
   {Uranus}.] (Chem.)
   An element of the chromium group, found in certain rare
   minerals, as pitchblende, uranite, etc., and reduced as a
   heavy, hard, nickel-white metal which is quite permanent. Its
   yellow oxide is used to impart to glass a delicate
   greenish-yellow tint which is accompanied by a strong
   fluorescence, and its black oxide is used as a pigment in
   porcelain painting. Symbol U. Atomic weight 239.

Source : WordNet®

uranium
     n : a heavy toxic silvery-white radioactive metallic element;
         occurs in many isotopes; used for nuclear fuels and
         nuclear weapons [syn: {U}, {atomic number 92}]