- Shock-like contraction of a portion of a muscle, an entire muscle, or a group of muscles; may be part of a disease process or a normal physiological response.
Definition from: CRISP Thesaurus via Unified Medical Language System at the National Library of Medicine
- Irregular involuntary contraction of a muscle usually resulting from functional disorder of controlling motor neurons; also: a condition characterized by myoclonus.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
See also Understanding Medical Terminology.