Source : Webster's Revised Unabridged Dictionary (1913)

Cerium \Ce"ri*um\, n. [Named by Berzelius in 1803 from the
   asteroid Ceres, then just discovered (1801).] (Chem.)
   A rare metallic element, occurring in the minerals cerite,
   allanite, monazite, etc. Symbol Ce. Atomic weight 141.5. It
   resembles iron in color and luster, but is soft, and both
   malleable and ductile. It tarnishes readily in the air.

Source : WordNet®

cerium
     n : a ductile gray metallic element of the lanthanide series;
         used in lighter flints; the most abundant of the
         rare-earth group [syn: {Ce}, {atomic number 58}]