The Collaborative International Dictionary of English v.0.48:

Titanium \Ti*ta"ni*um\, n. [NL., fr. L. Titani or Titanes, Gr.
   ?, the sons of the earth.] (Chem.)
   An elementary substance found combined in the minerals
   manaccanite, rutile, sphene, etc., and isolated as an
   infusible iron-gray amorphous powder, having a metallic
   luster. It burns when heated in the air. Symbol Ti. Atomic
   weight 48.1.
   [1913 Webster]

WordNet (r) 3.0 (2006):

titanium
    n 1: a light strong grey lustrous corrosion-resistant metallic
         element used in strong lightweight alloys (as for airplane
         parts); the main sources are rutile and ilmenite [syn:
         titanium, Ti, atomic number 22]

The Elements (07Nov00):

titanium
Symbol: Ti
Atomic number: 22
Atomic weight: 47.90
White metallic transition element. Occurs in numerous minerals. Used in
strong, light corrosion-resistant alloys. Forms a passive oxide coating
when exposed to air. First discovered by Gregor in 1789.