What is the definition or description of: muscle twitches?

Contractions: Muscle twitches are involuntary contractions. They are generally benign, but can be a sign of parkinson's disease, so if they persist, be seen.

Fasciculation: The twitches you can see and feel in muscle are contractions of irritable muscle fibers. They are sometimes seen with muscle fatigue. I sometimes see young people with fasciculations who google the word and come in afraid they have ALS . There is also an entity called benign fasciculation syndrome that is sometimes accompanied by cramping. Caffeine and theophylline (in tea) can provoke them.