The Collaborative International Dictionary of English v.0.48:

Vanadium \Va*na"di*um\, n. [NL., fr. Icel. Vanad[imac]s, a
   surname of the Scandinavian goddess Freya.] (Chem.)
   A rare element of the nitrogen-phosphorus group, found
   combined, in vanadates, in certain minerals, and reduced as
   an infusible, grayish-white metallic powder. It is
   intermediate between the metals and the non-metals, having
   both basic and acid properties. Symbol V (or Vd, rarely).
   Atomic weight 50.94 (C12=12.000).
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

vanadium
    n 1: a soft silvery white toxic metallic element used in steel
         alloys; it occurs in several complex minerals including
         carnotite and vanadinite [syn: vanadium, V, atomic
         number 23]

The Elements (07Nov00):

vanadium
Symbol: V
Atomic number: 23
Atomic weight: 50.9415
Soft and ductile, bright white metal. Good resistance to corrosion by
alkalis, sulphuric and hydrochloric acid. It oxidizes readily about
933K. There are two naturally occurring isotopes of vanadium, and 5
radioisotopes, V-49 having the longest half-life at 337 days. Vanadium
has nuclear applications, the foil is used in cladding titanium to
steel,
and vanadium-gallium tape is used to produce a superconductive magnet.
Originally discovered by Andres Manuel del Rio of Mexico City in 1801.
His discovery went unheeded, however, and in 1820, Nils Gabriel Sefstron
of Sweden rediscovered it. Metallic vanadium was isolated by Henry
Enfield
Roscoe in 1867. The name vanadium comes from Vanadis, a goddess of
Scandinavian mythology. Silvery-white metallic transition element.
Vanadium is essential to ascidians. Rats and chickens are also known
to require it. Metal powder is a fire hazard, and vanadium compounds
should be considered highly toxic. May cause lung cancer if inhaled.