verb
convulse
kuhn-VUHLS/kənˈvʌls/
To shake violently beyond normal control.
A caregiver stays nearby as the adult convulses on the floor.

Etymology
The Latin combination meant pulling this way and that or wrenching. That violent tugging image carries into sudden, involuntary contractions that make a body shake.
In context
A ghastly scream tore the air, the death-by-a-thousand-cuts agony making his whole body convulse.
More examples
- The sudden seizure caused his body to convulse.
- Violent coughing convulses his whole body.
- Her shoulders convulsed with uncontrollable laughter.
Forms
convulse · convulses · convulsed · convulsing
convulsion noun — A sudden, violent, involuntary muscular contraction.
convulsive adjective — Marked by sudden, uncontrollable muscular movements.