a corroding or sloughing ulcer; esp. a spreading gangrenous ulcer or collection of ulcers in or about the mouth; -- called also water canker, canker of the mouth, and noma.-anything which corrodes, corrupts, or destroy.-a disease incident to trees, causing the bark to rot and fall off.-an obstinate and often incurable disease of a horse's foot, characterized by separation of the horny portion and the development of fungoid growths; -- usually resulting from neglected thrush.-a kind of wild, worthless rose; the dog-rose.-to affect as a canker; to eat away; to corrode; to consume.-to infect or pollute; to corrupt.-to waste away, grow rusty, or be oxidized, as a mineral.-to be or become diseased, or as if diseased, with canker; to grow corrupt; to become venomous.