Definition of "convulsion"

It would seem as if calm were necessary to convulsion; for the tranquillity of the last few months was again to be disturbed by political commotion.

1834, L[etitia] E[lizabeth] L[andon], Francesca Carrara. […], volume III, London: Richard Bentley, […], (successor to Henry Colburn), pages 97–98

In a convulsion that has caught many in Brazil and beyond by surprise, waves of protesters denounced their leaders for dedicating so many resources to cultivating Brazil’s global image by building stadiums for international events, when basic services like education and health care remain woefully inadequate.

2013 June 18, Simon Romero, “Protests Widen as Brazilians Chide Leaders”, in New York Times, retrieved 21 June 2013