The Collaborative International Dictionary of English v.0.48:

Osteotomy \Os`te*ot"o*my\, n.
   1. The dissection or anatomy of bones; osteology.
      [1913 Webster]

   2. (Surg.) The operation of dividing a bone or of cutting a
      piece out of it, -- done to remedy deformity, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

osteotomy
    n 1: surgical sectioning of bone