caesium caesious • caesium clock · · · Info · Definitions · Synonyms · Characters · · caesium · · Text Latin · · Script 7 · · Length 3 · · Syllables Definitions · · · (noun) a soft silver-white ductile metallic element (liquid at normal temperatures); the most electropositive and alkaline metal. Synonyms: cesium, Cs, atomic number 55. · · Noun Definition 1 Synonyms · · · cesium · · Synonym 1 cs · · Synonym 2 atomic number 55 · · Synonym 3 Characters · · a latin small letter a U+0061 c latin small letter c U+0063 e latin small letter e U+0065 i latin small letter i U+0069 m latin small letter m U+006D s latin small letter s U+0073 u latin small letter u U+0075