WordNet (r) 3.0 (2006):

atomic number 12
    n 1: a light silver-white ductile bivalent metallic element; in
         pure form it burns with brilliant white flame; occurs
         naturally only in combination (as in magnesite and dolomite
         and carnallite and spinel and olivine) [syn: magnesium,
         Mg, atomic number 12]