Definition of cesium
: a silver-white soft ductile element of the alkali metal group that is the most electropositive element known and that is used especially in photoelectric cells — see element table
Recent Examples of cesium from the Web
Stuhlinger wrote that cesium would make a more efficient propellant than rubidium.
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Origin and Etymology of cesium
New Latin, from Latin caesius bluish gray
First Known Use: 1861
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