[ru.bid.i.um] n [NL, fr. L rubidus red, fr. rubere] (1861): a soft silvery metallic element of the alkali metal group that reacts violently with water and bursts into flame spontaneously in air
RUBIDIUM
Meaning of RUBIDIUM in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012