DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   ratter
       n 1: a disloyal person who betrays or deserts his cause or
            religion or political party or friend etc. [syn:
            deserter, apostate, renegade, turncoat, recreant,
            ratter]
       2: any of several breeds of terrier developed to catch rats
          [syn: rat terrier, ratter]