The Collaborative International Dictionary of English v.0.48:

Ulcerate \Ul"cer*ate\, v. i. [imp. & p. p. Ulcerated; p. pr. &
   vb. n. Ulcerating.] [L. ulceratus, p. p. of ulcerare, fr.
   ulcus ulcer.]
   To be formed into an ulcer; to become ulcerous.
   [1913 Webster]