(n)a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal, Syn.Cs, caesium, atomic number 55
n. the chemical element of atomic number 55. It is a univalent element, the most electropositive metal. Symbol Cs; atomic weight 132.905. IT has a melting point of 28.4° C. Syn. -- caesium, Cs. [ WordNet 1.5 ]