I. cae ‧ si ‧ um BrE AmE British English , cesium American English /ˈsiːziəm/ noun [uncountable]
[ Date: 1800-1900 ; Language: Latin ; Origin: caesius 'bluish grey' ]
a soft silver-white metal that is used in ↑ photoelectric cell s . It is a chemical ↑ element : symbol Cs
II. ce ‧ si ‧ um /ˈsiːziəm/ BrE AmE noun [uncountable]
the American spelling of ↑ caesium