The Collaborative International Dictionary of English v.0.48:

Writhe \Writhe\, v. t. [imp. Writhed; p. p. Writhed, Obs. or
   Poetic Writhen; p. pr. & vb. n. Writhing.] [OE. writhen,
   AS. wr[imac]?an to twist; akin to OHG. r[imac]dan, Icel.
   r[imac]?a, Sw. vrida, Dan. vride. Cf. Wreathe, Wrest,
   Wroth.]
   [1913 Webster]
   1. To twist; to turn; now, usually, to twist or turn so as to
      distort; to wring. "With writhing [turning] of a pin."
      --Chaucer.
      [1913 Webster]

            Then Satan first knew pain,
            And writhed him to and fro.           --Milton.
      [1913 Webster]

            Her mouth she writhed, her forehead taught to frown.
                                                  --Dryden.
      [1913 Webster]

            His battle-writhen arms, and mighty hands.
                                                  --Tennyson.
      [1913 Webster]

   2. To wrest; to distort; to pervert.
      [1913 Webster]

            The reason which he yieldeth showeth the least part
            of his meaning to be that whereunto his words are
            writhed.                              --Hooker.
      [1913 Webster]

   3. To extort; to wring; to wrest. [R.]
      [1913 Webster]

            The nobility hesitated not to follow the example of
            their sovereign in writhing money from them by every
            species of oppression.                --Sir W.
                                                  Scott.
      [1913 Webster]

WordNet (r) 3.0 (2006):

writhing
    adj 1: moving in a twisting or snake-like or wormlike fashion;
           "wiggly worms" [syn: wiggly, wriggling, wriggly,
           writhing]