Definition of "canker" [can•ker]

• Ulceration of the mouth and lips. (noun)
• An inflammation or infection of the ear and auditory canal, especially in dogs and cats. (noun)
• A condition in horses similar to but more advanced than thrush. (noun)
• A localized diseased or necrotic area on a plant part, especially on a trunk, branch, or twig of a woody plant, usually caused by fungi or bacteria. (noun)
• Any of several diseases of plants characterized by the presence of such lesions. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "I didn't mean to, Bill, but it's like a friggin 'canker sore."
• "Colonel Le Noir had not been destined soon to die; his wound, an inward canker from a copper bullet, that the surgeon had at length succeeded in extracting, took the form of a chronic fester disease."
• "Palestinian homes during the invasion of Gaza, the paper calls on Israel to root out what it calls the canker of brutality and ill-discipline from the military."