The Collaborative International Dictionary of English v.0.48:

Stapler \Sta"pler\ (-pl[~e]r), n.
   1. A dealer in staple goods.
      [1913 Webster]

   2. One employed to assort wool according to its staple.
      [1913 Webster]

   3. A device used to drive a staple[8] into objects so as to
      fasten them together.
      [PJC]

WordNet (r) 3.0 (2006):

stapler
    n 1: a machine that inserts staples into sheets of paper in
         order to fasten them together [syn: stapler, stapling
         machine]