The Collaborative International Dictionary of English v.0.48:

Tic \Tic\, n. [F.] (Med.)
   A local and habitual convulsive motion of certain muscles;
   especially, such a motion of some of the muscles of the face;
   twitching; velication; -- called also spasmodic tic.
   --Dunglison.
   [1913 Webster]

   Tic douloureux. [F., fr. tic a knack, a twitching +
      douloureux painful.] (Med.) Neuralgia in the face; face
      ague. See under Face.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tic
    n 1: a local and habitual twitching especially in the face