Definitions for caesiumˈsi zi əm
Random House Webster's College Dictionary
cae•si•umˈsi zi əm(n.)
Ref: cesium .
cesium, caesium, Cs, atomic number 55(noun)
a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal
A metallic chemical element (symbol Cs) with an atomic number of 55.
Origin: caesius, in reference to the radiation spectra + -ium
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 weight 132.6