The quality or state of being convulsive; the tendency to cause sudden, violent, involuntary movements or spasms.
From convulsive (from Latin convulsus, past participle of convellere 'to pull together') plus the suffix -ness indicating a state or quality. The word evolved to describe both physical spasms and figuratively, any sudden violent action or disturbance.
Convulsiveness appears frequently in 19th-century medical texts describing neurological conditions, but authors also used it poetically to describe social upheaval—revolutions were described as having 'convulsiveness' because they involved sudden, violent, involuntary upheaval of society, just like a person's body in seizure.
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