Source : Webster's Revised Unabridged Dictionary (1913)

Oncotomy \On*cot"o*my\ ([o^][ng]"k[o^]t*[-o]*m[y^]), n. [Gr.
   'o`gkos bulk, mass + te`mnein to cut: cf. F. oncotomie.]
   (Surg.)
   The opening of an abscess, or the removal of a tumor, with a
   cutting instrument. [Written also {onkotomy}.] --Dunglison.