The Collaborative International Dictionary of English v.0.48:

Neodymium \Ne`o*dym"i*um\, n. [NL. Dee Neo-, and Didymium.]
   (Chem.)
   The chemical element of atomic number 60, one of the rare
   earth elements. Symbol Nd. Atomic weight 144.27.

   Note: It is a rare metallic element occurring in combination
         with cerium, lanthanum, and other rare metals, and
         forming amethyst-colored salts. It was originally
         thought to be part of a supposed new element didymium,
         obtained from cerite in 1843. Later this was resolved
         into two elements, neodymium and praesodymium by von
         Welsbach in 1885. It is chiefly trivalent. It is a
         faintly yellow metal.
         [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

neodymium
    n 1: a yellow trivalent metallic element of the rare earth
         group; occurs in monazite and bastnasite in association
         with cerium and lanthanum and praseodymium [syn:
         neodymium, Nd, atomic number 60]

The Elements (07Nov00):

neodymium
Symbol: Nd
Atomic number: 60
Atomic weight: 144.24
Soft bright silvery metallic element, belongs to the lanthanoids. Seven
natural
isotopes, Nd-144 being the only radioactive one with a half-life of
10^10
to 10^15 years. Six artificial radioisotopes have been produced. The
metal is used in glass works to color glass a shade of violet-purple and
make it dichroic. One of the more reactive rare-earth metals, quickly
reacts
with air. Used in some rare-earth alloys. Neodymium is used to color
the glass used in welders' glasses. Neodymium is also used in very
powerful, permanent magnets (Nd2Fe14B). Discovered by Carl F. Auer von
Welsbach in Austria in 1885 by separating didymium into its elemental
components praseodymium and neodymium. The name comes from the Greek
words
"neos didymos" which means "new twin". Neodymium should be considered
highly toxic, however evidence would seem to show that it acts as little
more than a skin and eye irritant. The dust however, presents a fire and
explosion hazard.