The Collaborative International Dictionary of English v.0.48:

Chromium \Chro"mi*um\, n. [NL., fr. Gr. ? color.] (Chem.)
   A comparatively rare element occurring most abundantly in the
   mineral chromite. Atomic weight 52.5. Symbol Cr. When
   isolated it is a hard, brittle, grayish white metal, fusible
   with difficulty. Its chief commercial importance is for its
   compounds, as potassium chromate, lead chromate, etc., which
   are brilliantly colored and are used dyeing and calico
   printing. Called also chrome.
   [1913 Webster]

WordNet (r) 3.0 (2006):

chromium
    n 1: a hard brittle multivalent metallic element; resistant to
         corrosion and tarnishing [syn: chromium, Cr, atomic
         number 24]

The Elements (07Nov00):

chromium
Symbol: Cr
Atomic number: 24
Atomic weight: 51.996
Hard silvery transition element. Used in decorative electroplating.
Discovered in 1797 by Vauquelin.