The Collaborative International Dictionary of English v.0.48:

Zirconium \Zir*co"ni*um\, n. [NL.] (Chem.)
   A rare element of the carbon-silicon group, intermediate
   between the metals and nonmetals, obtained from the mineral
   zircon as a dark sooty powder, or as a gray metallic
   crystalline substance. Symbol Zr. Atomic weight, 90.4.
   [1913 Webster]

WordNet (r) 3.0 (2006):

zirconium
    n 1: a lustrous grey strong metallic element resembling
         titanium; it is used in nuclear reactors as a neutron
         absorber; it occurs in baddeleyite but is obtained chiefly
         from zircon [syn: zirconium, Zr, atomic number 40]

The Elements (07Nov00):

zirconium
Symbol: Zr
Atomic number: 40
Atomic weight: 91.22
Grey-white metallic transition element. Five natural isotopes and six
radioactive isotopes are known. Used in nuclear reactors for a neutron
absorber. Discovered in 1789 by Martin Klaproth, isolated in 1824 by
Berzelius.