Involuntary movement (3)

I believe the answer is:
tic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">involuntary movement</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tic that I've seen before include "Involuntary muscular spasm" , "Twitch in analytical way" , "Nervous habit" , "Convulsive spasm" , "Involuntary twitch" .)