Source : Webster's Revised Unabridged Dictionary (1913)

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®

wrenching
     adj : causing great physical or mental suffering; "a wrenching
           pain" [syn: {racking}]