DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   prion
       n 1: (microbiology) an infectious protein particle similar to a
            virus but lacking nucleic acid; thought to be the agent
            responsible for scrapie and other degenerative diseases of
            the nervous system