The Collaborative International Dictionary of English v.0.48:

Trypsin \Tryp"sin\, n. [Gr. ? a rubbing, fr. ? to rub, grind. So
   called because it causes protein to break up or to fall
   apart.] (physiol.)
   A proteolytic enzyme present in the pancreatic juice. Unlike
   the pepsin of the gastric juice, it acts in a neutral or
   alkaline fluid, and not only converts the albuminous matter
   of the food into soluble peptones, but also, in part, into
   leucin and tyrosin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trypsin
    n 1: an enzyme of pancreatic origin; catalyzes the hydrolysis of
         proteins to smaller polypeptide units