terbium

Ter"bi*um, n. Etym: [NL., fr. Ytterby, in Sweden. See Erbium.] (Chem.) Defn: A rare metallic element, of uncertain identification, supposed to exist in certain minerals, as gadolinite and samarskite, with other rare ytterbium earth. Symbol Tr or Tb. Atomic weight 150.

---