rubidium-strontium noun[before a noun]1 •Designating a method of geological dating based on the relative amounts in rock of rubidium-87 and its beta-decay product, strontium-87.Isotopic dating of meteorites using the rubidium-strontium system and others indicates that the most primitive rocks in the solar system are 4.56 billion years old, determined rather precisely. — 1999
