The Collaborative International Dictionary of English v.0.48:

Overreach \O"ver*reach`\ ([=o]"v[~e]r*r[=e]ch`), n.
   The act of striking the heel of the fore foot with the toe of
   the hind foot; -- said of horses.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overreach \O`ver*reach"\ ([=o]`v[~e]r*r[=e]ch"), v. t. [imp. &
   p. p. Overreached, (Overraught, obs.); p. pr. & vb. n.
   Overreaching.]
   [1913 Webster]
   1. To reach above or beyond in any direction.
      [1913 Webster]

   2. To deceive, or get the better of, by artifice or cunning;
      to outwit; to cheat. --Shak.
      [1913 Webster]

   3. To defeat one's own purpose by trying to do too much or by
      trying too hard or with excessive eagerness; -- used
      reflexively; as, the candidate overreached himself by
      trying to plant false rumors, which backfired/
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Overreach \O`ver*reach"\, v. i.
   1. To reach too far; as:
      (a) To strike the toe of the hind foot against the heel or
          shoe of the forefoot; -- said of horses.
      (b) (Naut.) To sail on one tack farther than is necessary.
          --Shak.
          [1913 Webster]

   2. To cheat by cunning or deception.
      [1913 Webster]

WordNet (r) 3.0 (2006):

overreach
    v 1: fail by aiming too high or trying too hard
    2: beat through cleverness and wit; "I beat the traffic"; "She
       outfoxed her competitors" [syn: outwit, overreach,
       outsmart, outfox, beat, circumvent]