Twitch

twitch
1. The act of twitching; a pull with a jerk; a short, sudden, quick pull; as, a twitch by the sleeve.
2. A short, spastic contraction of the fibres or muscles; a simple muscular contraction; as, convulsive twitches; a twitch in the side.
3. (Science: veterinary) 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.