v.
  - make or cause to make a short, sudden jerking movement.
- use a twitch to subdue (a horse).
n.
   - a twitching movement.
- a pang:![]()  he felt a twitch of annoyance. 
- a small noose attached to a stick, which may be twisted around the upper lip or ear of a horse to subdue it during veterinary procedures.
Etymology
  ME: of Gmc origin; rel. to OE twiccian ‘to pluck, pull sharply’.