Source : Webster's Revised Unabridged Dictionary (1913)

Palladium \Pal*la"di*um\, n. [L., fr. Gr. ?, fr. ?, ?, Pallas.]
   1. (Gr. Antiq.) Any statue of the goddess Pallas; esp., the
      famous statue on the preservation of which depended the
      safety of ancient Troy.

   2. Hence: That which affords effectual protection or
      security; a sateguard; as, the trial by jury is the
      palladium of our civil rights. --Blackstone.

Palladium \Pal*la"di*um\, n. [NL.] (Chem.)
   A rare metallic element of the light platinum group, found
   native, and also alloyed with platinum and gold. It is a
   silver-white metal resembling platinum, and like it permanent
   and untarnished in the air, but is more easily fusible. It is
   unique in its power of occluding hydrogen, which it does to
   the extent of nearly a thousand volumes, forming the alloy
   {Pd2H}. It is used for graduated circles and verniers, for
   plating certain silver goods, and somewhat in dentistry. It
   was so named in 1804 by Wollaston from the asteroid Pallas,
   which was discovered in 1802. Symbol Pd. Atomic weight,
   106.2.

Source : WordNet®

palladium
     n : a silver-white metallic element of the platinum group that
         resembles platinum; occurs in some copper and nickel
         ores; does not tarnish at ordinary temperatures and is
         used (alloyed with gold) in jewelry [syn: {Pd}, {atomic
         number 46}]