Source : Webster's Revised Unabridged Dictionary (1913)

Dysprosium \Dys*pro"si*um\, n. [NL., fr. Gr. dyspro`sitos hard
   to get at.] (Chem.)
   An element of the rare earth-group. Symbol Dy; at. wt.,
   162.5.

Source : WordNet®

dysprosium
     n : a trivalent metallic element of the rare earth group; forms
         compounds that are highly magnetic [syn: {Dy}, {atomic
         number 66}]