rubidium

n. [ NL., fr. L. rubidus red, fr. rubere to be red. So called from two dark red spectroscopic lines by means of which it was discovered in the lepidolite from Rozena, Moravia. See Rubicund. ] (Chem.) A rare metallic element of the alkali metal series, atomic number 37. It occurs quite widely, but in small quantities, and always combined. It is isolated as a soft yellowish white metal, analogous to potassium in most of its properties. Symbol Rb. Atomic weight, 85.48. [ 1913 Webster ]