Petit mal: A form of epilepsy with very brief, unannounced lapses in consciousness. A petit mal seizure involves a brief loss of awareness, which can be accompanied by blinking or mouth twitching. Petit mal seizures have a very characteristic appearance on an electroencephalogram (EEG).
Petit mal (little illness in French) seizures are also known as absence seizures. Petit mal seizures take the form of a staring spell: the person suddenly seems to be "absent."