Source : Webster's Revised Unabridged Dictionary (1913)

Erbium \Er"bi*um\, n. [NL. Named from Ytterby, in Sweden, where
   gadolinite is found. Cf. {Terbium}, {Yttrium}, {Ytterbium}.]
   (Chem.)
   A metallic element of the rare earth group, found in
   gadolinite and some other minerals. Symbol, Er; at. wt.
   167.4. Its salts are rose-colored and give characteristic
   spectra.

Erbium \Er"bi*um\, n. [NL. from Ytterby, in Sweden, where
   gadolinite is found. Cf. {Terbium}, {Yttrium}, {Ytterbium}.]
   (Chem.)
   A rare metallic element associated with several other rare
   elements in the mineral gadolinite from Ytterby in Sweden.
   Symbol Er. Atomic weight 165.9. Its salts are rose-colored
   and give characteristic spectra. Its sesquioxide is called
   erbia.

Source : WordNet®

erbium
     n : a trivalent metallic element of the rare earth group; occurs
         with yttrium [syn: {Er}, {atomic number 68}]