n. 1 (usu. in pl.) violent irregular motion of a limb or limbs or the body caused by involuntary contraction of muscles, esp. as a disorder of infants. 2 a violent natural disturbance, esp. an earthquake. 3 violent social or political agitation. 4 (in pl.) uncontrollable laughter. convulsionary adj.
[ F convulsion or L convulsio (as CONVULSE) ]