Cushing's ulcer: A type of gastrointestinal ulcer associated with stressful medical conditions of the brain, in particular, trauma (accidents), operations, or strokes. The ulcers occur more commonly in the stomach than the duodenum. Although the ulcers usually do not cause symptoms, complications include bleeding and perforation. The cause of stress ulcers such as Cushing's ulcers is not known, but increased secretion of acid in the stomach is important in their development, and prevention and treatment generally is directed at neutralizing or preventing the secretion of acid.