大だい発ほっ作さだいほっさMeanings1noungrand mal seizure; tonic-clonic seizureMedical term for a major epileptic seizure involving loss of consciousness and convulsions. Contrasts with 小発作 (petit mal seizure).See also: 小発作彼かれは大だい発ほっ作さを起おこして倒たおれた。He collapsed from a grand mal seizure.