Source : Webster's Revised Unabridged Dictionary (1913)

Vellication \Vel`li*ca"tion\, [L. vellicatio.]
   1. The act of twitching, or of causing to twitch.

   2. (Med.) A local twitching, or convulsive motion, of a
      muscular fiber, especially of the face.

Source : WordNet®

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