Source : Webster's Revised Unabridged Dictionary (1913)

Ulcer \Ul"cer\, n. [F. ulc[`e]re, L. ulcus, gen. ulceris, akin
   to Gr. ?.]
   1. (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. Fig.: Anything that festers and corrupts like an open
      sore; a vice in character.

   {Cold ulcer} (Med.), an ulcer on a finger or toe, due to
      deficient circulation and nutrition. In such cases the
      extremities are cold.

Ulcer \Ul"cer\, v. t.
   To ulcerate. [R.] --Fuller.

Source : WordNet®

ulcer
     n : a circumscribed inflammatory and often suppurating lesion on
         the skin or an internal mucous surface resulting in
         necrosis of tissue [syn: {ulceration}]