an ulcer or spreading sore, esp one affecting the mouth
an area of dead tissue or an open wound in a plant
as killing as the canker to the rose — Milton
any of various inflammatory diseases of animals, e.g. an ear disease of dogs, cats, and rabbits, or a disease of horses that softens the underside of the hooves
a source of spreading corruption or evil
cankerous /-rəs/ adj
[Middle English via French from Latin cancer crab, cancer]