The Collaborative International Dictionary of English v.0.48:

Retractor \Re*tract"or\ (r[-e]*tr[=a]kt"[~e]r), n.
   One who, or that which, retracts. Specifically:
   (a) In breech-loading firearms, a device for withdrawing a
       cartridge shell from the barrel.
   (b) (Surg.) An instrument for holding apart the edges of a
       wound during amputation.
   (c) (Surg.) A bandage to protect the soft parts from injury
       by the saw during amputation.
   (d) (Anat. & Zool.) A muscle serving to draw in any organ or
       part. See Illust. under Phylactolaemata.
       [1913 Webster]

WordNet (r) 3.0 (2006):

retractor
    n 1: surgical instrument that holds back the edges of a surgical
         incision