The Collaborative International Dictionary of English v.0.48:

Twitch \Twitch\, v. t. [imp. & p. p. Twitched; p. pr. & vb. n.
   Twitching.] [OE. twicchen, fr. (doubtful) AS. twiccian;
   akin to AS. angeltwicca a worm used for bait, literally, a
   hook twitcher, LG. twikken to tweak, G. zwicken. Cf.
   Tweak.]
   To pull with a sudden jerk; to pluck with a short, quick
   motion; to snatch; as, to twitch one by the sleeve; to twitch
   a thing out of another's hand; to twitch off clusters of
   grapes.
   [1913 Webster]

         Thrice they twitched the diamond in her ear. --Pope.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Twitch \Twitch\, n.
   1. The act of twitching; a pull with a jerk; a short, sudden,
      quick pull; as, a twitch by the sleeve.
      [1913 Webster]

   2. A short, spastic contraction of the fibers or muscles; a
      simple muscular contraction; as, convulsive twitches; a
      twitch in the side.
      [1913 Webster]

   3. (Far.) A stick with a hole in one end through which passes
      a loop, which can be drawn tightly over the upper lip or
      an ear of a horse. By twisting the stick the compression
      is made sufficiently painful to keep the animal quiet
      during a slight surgical operation. --J. H. Walsh.
      [1913 Webster]

WordNet (r) 3.0 (2006):

twitch
    n 1: a sudden muscle spasm; especially one caused by a nervous
         condition [syn: twitch, twitching, vellication]
    v 1: make an uncontrolled, short, jerky motion; "his face is
         twitching" [syn: twitch, jerk]
    2: move with abrupt, seemingly uncontrolled motions; "The
       patient's legs were jerkings" [syn: jerk, twitch]
    3: toss with a sharp movement so as to cause to turn over in the
       air [syn: flip, twitch]
    4: squeeze tightly between the fingers; "He pinched her behind";
       "She squeezed the bottle" [syn: pinch, squeeze, twinge,
       tweet, nip, twitch]
    5: move or pull with a sudden motion