1. An emotionally unstable condition brought about by a traumatic experience.
2. A state of extreme, or exaggerated, emotion; such as, excitement or panic; especially, among large numbers of people.
3. Behavior exhibiting excessive or uncontrollable emotion; such as, fear or panic; or uncontrollable laughter or crying.
4. A mental disorder characterized by emotional excitability and sometimes by amnesia or a physical deficit; such as, paralysis, or a sensory deficit, without an organic cause.
5. A psychoneurotic disorder characterized by violent emotional outbreaks, disturbances of sensory and motor functions, and various abnormal effects due to autosuggestion.

The term "hysteria" comes from the ancient idea that it was in some way associated with the female uterus or womb.

The old-fashioned association of hysteria with women, and with their supposed sexual disturbances, is no longer considered to be a valid cause of any hysterical conditions.

Hysteria in a group of people, usually closely associated in a school or workplace.

The inciting incident might be a rumor or an unaccustomed odor; such as, paint fumes in a workplace.