ulcer

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A lesion of the skin or a mucous membrane such as the one lining the stomach or duodenum that is accompanied by formation of pus and necrosis of surrounding tissue, usually resulting from inflammation or ischemia.
2. n. A corrupting condition or influence.

Century Dictionary and Cyclopedia

1. n. A sore in any of the soft parts of the body, open either to the surface or to some natural cavity, and attended with a secretion of pus or some kind of discharge; a solution of continuity of the skin of the body, or of the investing tissue of any natural cavity, the result of morbid action, not of mechanical injury nor of a healthy reparative process. A wound may become an ulcer, but is not such unless diseased action is set up. An abscess is an ulceration within the tissue of a part which has formed a morbid excavation with a contracted orifice or none. Ulcers have been divided into local and constitutional, but the distinction is not obvious. They are also treated as simple or specific sores. Most ulcers are both constitutional and specific—that is, the local exhibition of a specific poison which infects the whole system, as the diphtheritic, the syphilitic, or the carcinomatous; others are less obviously specific, as the scrofulous or the scorbutic.
2. n. Hence, figuratively, a sore, blot, stain, or cause of reproach, in an ethical sense: as, an ulcer of the body politic.
3. To ulcerate. Fuller, Holy and Profane State, V. vi. 3.

Wiktionary

1. n. pathology An open sore of the skin, eyes or mucous membrane, often caused by an initial abrasion and generally maintained by an inflammation and/or an infection.

GNU Webster's 1913

1. n. (Med.) A solution of continuity in any of the soft parts of the body, discharging purulent matter, found on a surface, especially one of the natural surfaces of the body, and originating generally in a constitutional disorder; a sore discharging pus. It is distinguished from an abscess, which has its beginning, at least, in the depth of the tissues.
2. n. Fig.: Anything that festers and corrupts like an open sore; a vice in character.
3. v. rare To ulcerate.

WordNet 3.0

1. n. a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue