Source : Webster's Revised Unabridged Dictionary (1913)

Convulsion \Con*vul"sion\, n. [L. convulsio: cf. F. convulsion.]
   1. (Med.) An unnatural, violent, and unvoluntary contraction
      of the muscular parts of an animal body.

   2. Any violent and irregular motion or agitation; a violent
      shaking; a tumult; a commotion.

            Those two massy pillars, With horrible convulsion,
            to and fro He tugged, he shook, till down they came.
                                                  --Milton.

            Times of violence and convulsion.     --Ames.

   Syn: Agitation; commotion; tumult; disturbance.

Source : WordNet®

convulsion
     n 1: a sudden uncontrollable attack; "a paroxysm of giggling"; "a
          fit of coughing"; "convulsions of laughter" [syn: {paroxysm},
           {fit}]
     2: violent uncontrollable contractions of muscles
     3: a violent disturbance; "the convulsions of the stock market"
        [syn: {turmoil}, {upheaval}]
     4: a physical disturbance such as an earthquake or upheaval