The Collaborative International Dictionary of English v.0.48:

Palladium \Pal*la"di*um\ (p[a^]l*l[=a]"d[i^]*[u^]m), n. [L., fr.
   Gr. Palla`dion, fr. Palla`s, Palla`dos, Pallas.]
   [1913 Webster]
   1. (Gr. Antiq.) Any statue of the goddess Pallas; esp., the
      famous statue on the preservation of which depended the
      safety of ancient Troy.
      [1913 Webster]

   2. Hence: That which affords effectual protection or
      security; a safeguard; as, the trial by jury is the
      palladium of our civil rights. --Blackstone.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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, with
   a melting point of 1555[deg] C. It can also be prepared as a
   finely divided black powder. It is unique in its power of
   absorbing 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 number, 46. Atomic weight, 106.42.
   Density 12.0.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pd \Pd\ prop. n.
   The chemical symbol for palladium, an element of the
   platinum group, of atomic number 46.

   Syn: palladium.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

palladium
    n 1: 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: palladium, Pd,
         atomic number 46]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "palladium":
   aegis, arm guard, backstop, buffer, bulwark, bumper, contraceptive,
   copyright, crash helmet, cushion, dashboard, dodger, face mask,
   fender, finger guard, foot guard, fuse, goggles, governor, guard,
   guardrail, hand guard, handrail, hard hat, helmet, insulation,
   interlock, knee guard, knuckle guard, laminated glass,
   life preserver, lifeline, lightning conductor, lightning rod, mask,
   mudguard, nose guard, pad, padding, patent, pilot, preventive,
   prophylactic, protective clothing, protective umbrella, safeguard,
   safety, safety glass, safety plug, safety rail, safety shoes,
   safety switch, safety valve, screen, seat belt, shield, shin guard,
   sun helmet, umbrella, windscreen, windshield



The Elements (07Nov00):

palladium
Symbol: Pd
Atomic number: 46
Atomic weight: 106.4
Soft white ductile transition element. Found with some copper and nickel
ores. Does not react with oxygen at normal temperatures. Dissolves
slowly
in hydrochloric acid. Discovered in 1803 by W.H. Wollaston.