The Collaborative International Dictionary of English v.0.48:

Rhodium \Rho"di*um\, n. [NL., fr. Gr. "ro`don the rose. So
   called from the rose-red color of certain of its solutions.
   See Rhododendron.] (Chem.)
   A rare element of the light platinum group. It is found in
   platinum ores, and obtained free as a white inert metal which
   it is very difficult to fuse. Symbol Rh. Atomic weight 104.1.
   Specific gravity 12.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rhodium
    n 1: a white hard metallic element that is one of the platinum
         group and is found in platinum ores; used in alloys with
         platinum [syn: rhodium, Rh, atomic number 45]

The Elements (07Nov00):

rhodium
Symbol: Rh
Atomic number: 45
Atomic weight: 102.905
Silvery white metallic transition element. Found with platinum and used
in
some platinum alloys. Not attacked by acids, dissolves only in aqua
regia.
Discovered in 1803 by W.H. Wollaston.