Noun rb has 1 sense
  1. rubidium, Rb, atomic number 37 - a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite
    --1 is a kind of metallic element, metal
    --1 is a substance of carnallite; lepidolite; pollucite
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