Source : Webster's Revised Unabridged Dictionary (1913)

Wrench \Wrench\ (r[e^]nch), n. [OE. wrench deceit, AS. wrenc
   deceit, a twisting; akin to G. rank intrigue, crookedness,
   renken to bend, twist, and E. wring. [root]144. See {Wring},
   and cf. {Ranch}, v. t.]
   1. Trick; deceit; fraud; stratagem. [Obs.]

            His wily wrenches thou ne mayst not flee. --Chaucer.

   2. A violent twist, or a pull with twisting.

            He wringeth them such a wrench.       --Skelton.

            The injurious effect upon biographic literature of
            all such wrenches to the truth, is diffused
            everywhere.                           --De Quincey.

   3. A sprain; an injury by twisting, as in a joint.

   4. Means; contrivance. [Obs.] --Bacon.

   5. An instrument, often a simple bar or lever with jaws or an
      angular orifice either at the end or between the ends, for
      exerting a twisting strain, as in turning bolts, nuts,
      screw taps, etc.; a screw key. Many wrenches have
      adjustable jaws for grasping nuts, etc., of different
      sizes.

   6. (Mech.) The system made up of a force and a couple of
      forces in a plane perpendicular to that force. Any number
      of forces acting at any points upon a rigid body may be
      compounded so as to be equivalent to a wrench.

   {Carriage wrench}, a wrench adapted for removing or
      tightening the nuts that confine the wheels on the axles,
      or for turning the other nuts or bolts of a carriage or
      wagon.

   {Monkey wrench}. See under {Monkey}.

   {Wrench hammer}, a wrench with the end shaped so as to admit
      of being used as a hammer.

Wrench \Wrench\, v. t. [imp. & p. p. {Wrenched}; p. pr. & vb. n.
   {Wrenching}.] [OE. wrenchen, AS. wrencan to deceive,
   properly, to twist, from wrenc guile, deceit, a twisting.
   ????. See {Wrench}, n.]
   1. To pull with a twist; to wrest, twist, or force by
      violence.

            Wrench his sword from him.            --Shak.

            Forthwith this frame of mine was wrenched With a
            woeful agony.                         --Coleridge.

   2. To strain; to sprain; hence, to distort; to pervert.

            You wrenched your foot against a stone. --Swift.

Source : WordNet®

wrench
     n 1: a sharp strain on muscles or ligaments; "the wrench to his
          knee occurred as he fell"; "he was sidelined with a
          hamstring pull" [syn: {twist}, {pull}]
     2: a jerky pulling movement [syn: {twist}]
     3: a hand tool that is used to hold or twist a nut or bolt
        [syn: {spanner}]
     v 1: twist or pull violently or suddenly, especially so as to
          remove (something) from that to which it is attached or
          from where it originates; "wrench a window off its
          hinges"; "wrench oneself free from somebody's grip"; "a
          deep sigh was wrenched from his chest" [syn: {twist}]
     2: make a sudden twisting motion
     3: twist and compress, as if in pain or anguish; "Wring one's
        hand" [syn: {wring}]
     4: twist suddenly so as to sprain; "wrench one's ankle"; "The
        wrestler twisted his shoulder"; "the hikers sprained their
        ankles when they fell"; "I turned my ankle and couldn't
        walk for several days" [syn: {twist}, {sprain}, {turn}, {wrick},
         {rick}]