The Collaborative International Dictionary of English v.0.48:

Trephine \Tre*phine"\ (?; 277), n. [A dim. of 1st trepan: cf. F.
   tr['e]phine.] (Surg.)
   An instrument for trepanning, being an improvement on the
   trepan. It is a circular or cylindrical saw, with a handle
   like that of a gimlet, and a little sharp perforator called
   the center pin.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Trephine \Tre*phine"\, v. t. [imp. & p. p. Trephined; p. pr. &
   vb. n. Trephining.]
   To perforate with a trephine; to trepan.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trephine
    n 1: a surgical instrument used to remove sections of bone from
         the skull [syn: trepan, trephine]
    v 1: operate on with a trephine