The Collaborative International Dictionary of English v.0.48:

Wood tick \Wood" tick`\ (Zool.)
   Any one of several species of ticks of the genus Ixodes
   whose young cling to bushes, but quickly fasten themselves
   upon the bodies of any animal with which they come in
   contact. When they attach themselves to the human body they
   often produce troublesome sores. The common species of the
   Northern United States is Ixodes unipunctata.
   [1913 Webster]