A petit mal seizure is the term commonly given to a staring spell, most commonly called an "absence seizure." It is a brief (usually less than 15 seconds) disturbance of brain function due to abnormal electrical activity in the brain.
Petit mal seizures occur most commonly in people under age 20, usually in children ages 6 to 12. They can occur as the only type of seizure but can also happen along with other types of seizures such as generalized tonic-clonic seizures (also called grand mal seizures), twitches or jerks (myoclonus), or sudden loss of muscle strength (atonic seizures).
For more information, see:
Epilepsy Seizures Generalized tonic-clonic seizure Partial (focal) seizure
Seizure - petit mal; Absence seizure; Seizure - absence