Source : Webster's Revised Unabridged Dictionary (1913)

Osteoma \Os`te*o"ma\, n.; pl. {Osteomata}. [NL. See {Osteo-},
   and {-oma}.] (Med.)
   A tumor composed mainly of bone; a tumor of a bone.

Source : WordNet®

osteoma
     n : a slow growing benign tumor of consisting of bone tissue;
         usually on the skull or mandible
     [also: {osteomata} (pl)]