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]

WordNet (r) 3.0 (2006):

twitching
    n 1: a sudden muscle spasm; especially one caused by a nervous
         condition [syn: twitch, twitching, vellication]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "twitching":
   abstraction, abulia, agitation, alienation, anxiety,
   anxiety equivalent, anxiety state, apathy, apprehensiveness,
   attack of nerves, buck fever, case of nerves, catatonic stupor,
   compulsion, convulsive, dejection, depression, detachment,
   eclamptic, elation, emotionalism, euphoria, excessive irritability,
   fear, fidgetiness, fidgets, fidgety, fitful, folie du doute,
   formication, hypochondria, hysteria, hysterics, indifference,
   insensibility, itchiness, jerking, jerky, jiggety, jumpy, lethargy,
   mania, melancholia, mental distress, morbid excitability, nerves,
   nervosity, nervous stomach, nervousness, obsession, orgasmic,
   panic, panickiness, pathological indecisiveness, preoccupation,
   pruritus, psychalgia, psychomotor disturbance, saltatory,
   spasmodic, spastic, spell of nerves, stage fright, state of nerves,
   stupor, tic, trepidation, twitchety, twitchy, uneasiness,
   unresponsiveness, vellication, vellicative, withdrawal