(n)a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal, Syn.Cs, caesium, atomic number 55
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
n. [ NL., from L. caesius bluish gray. ] (Chem.) A rare alkaline metal found in mineral water; -- so called from the two characteristic blue lines in its spectrum. It was the first element discovered by spectrum analysis, and is the most strongly basic and electro-positive substance known. Symbol Cs. Atomic number 55. Atomic weight 132.6. Syn. -- cesium, Cs [ 1913 Webster ]