Source : Webster's Revised Unabridged Dictionary (1913)

Trypsinogen \Tryp*sin"o*gen\, n. [Trypsin + -gen.] (Physiol.)
   The antecedent of trypsin, a substance which is contained in
   the cells of the pancreas and gives rise to the trypsin.

Source : WordNet®

trypsinogen
     n : inactive precursor of trypsin; a substance secreted by the
         pancreas and converted to active trypsin by enterokinase
         in the small intestine