The Collaborative International Dictionary of English v.0.48:

Tracker \Track"er\, n.
   1. One who, or that which, tracks or pursues, as a man or dog
      that follows game.
      [1913 Webster]

            And of the trackers of the deer
            Scarce half the lessening pack was near. --Sir W.
                                                  Scott.
      [1913 Webster]

   2. (Mus.) In the organ, a light strip of wood connecting (in
      path) a key and a pallet, to communicate motion by
      pulling.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tracker
    n 1: someone who tracks down game