noun (n)

• a sudden uncontrollable attack(noun.state)

  Example:
  Convulsions of laughter.
  

  Synonym:
  fit, paroxysm
  

  source: wordnet30
• violent uncontrollable contractions of muscles(noun.state)

  source: wordnet30
• a violent disturbance(noun.state)

  Example:
  The convulsions of the stock market.
  

  Synonym:
  turmoil, upheaval
  

  source: wordnet30
• a physical disturbance such as an earthquake or upheaval(noun.event)

  source: wordnet30
• An unnatural, violent, and unvoluntary contraction of the muscular parts of an animal body.(noun)

  source: webster1913