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]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "overreach":
   aggrandize, amplify, ballyhoo, bamboozle, beat, beguile, betray,
   bilk, bluff, build up, burlesque, cajole, caricature,
   carry too far, cheat on, chouse, circumvent, conjure, cozen,
   deceive, defraud, delude, diddle, do, double-cross,
   draw the longbow, dupe, elude, evade, exaggerate, exceed, flimflam,
   foil, forestall, frustrate, gammon, get around, get round,
   give the runaround, give the slip, go beyond, go one better,
   go to extremes, gull, gyp, have, hoax, hocus-pocus, hornswaggle,
   humbug, hyperbolize, juggle, lay it on, let down, magnify,
   make much of, mock, outfigure, outflank, outfox, outgeneral,
   outguess, outmaneuver, outplay, outreach, outsmart, outwit,
   overcharge, overdo, overdraw, overestimate, overgo, overjump,
   overleap, overpass, overpraise, overreact, overrun, oversell,
   overshoot, overshoot the field, overshoot the mark, overspeak,
   overstate, overstep, overstress, overstride, pass, pass the buck,
   pigeon, pile it on, play one false, puff, put something over, snow,
   stonewall, stretch, stretch the truth, string along, superabound,
   surpass, take in, talk big, talk in superlatives, tout, transcend,
   travesty, trick, two-time, undo, victimize