DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   canker
       n 1: a fungal disease of woody plants that causes localized
            damage to the bark
       2: an ulceration (especially of the lips or lining of the mouth)
          [syn: canker, canker sore]
       3: a pernicious and malign influence that is hard to get rid of;
          "racism is a pestilence at the heart of the nation";
          "according to him, I was the canker in their midst" [syn:
          pestilence, canker]
       v 1: become infected with a canker
       2: infect with a canker