Source : Webster's Revised Unabridged Dictionary (1913)

Collagen \Col"la*gen\, n. [Gr. ko`lla glue + -gen.] (Physiol.
   Chem.)
   The chemical basis of ordinary connective tissue, as of
   tendons or sinews and of bone. On being boiled in water it
   becomes gelatin or glue.

Source : WordNet®

collagen
     n : a fibrous scleroprotein in bone and cartilage and tendon and
         other connective tissue; yields gelatin on boiling