The Collaborative International Dictionary of English v.0.48:

Ulceration \Ul`cer*a"tion\, n. [L. ulceratio: cf. F.
   ulc['e]ration.] (Med.)
   The process of forming an ulcer, or of becoming ulcerous; the
   state of being ulcerated; also, an ulcer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ulceration
    n 1: a circumscribed inflammatory and often suppurating lesion
         on the skin or an internal mucous surface resulting in
         necrosis of tissue [syn: ulcer, ulceration]
    2: the process of ulcer formation; the process of becoming
       ulcerated