pathologic lesion with disruption of skin, mucous membrane and extending into underlying tissue: ulcus ventriculi gastric ulcer; prepyloric u. prepyloric and pyloric ulcer are used synonymously in English to denote an ulcer within the pylorus proximal to the pyloric valve; pyloric u. see prepyloric u.; u. duodeni duodenal ulcer; u. perforans perforated ulcer; u. cruris decubital ulcer of legs.