/hi ster"ee euh, -stear"-/ , n.
1. an uncontrollable outburst of emotion or fear, often characterized by irrationality, laughter, weeping, etc.
2. Psychoanal. a psychoneurotic disorder characterized by violent emotional outbreaks, disturbances of sensory and motor functions, and various abnormal effects due to autosuggestion.
3. Psychiatry. See conversion disorder . Cf. mass hysteria .
[ 1795-1805; HYSTER(IC) + -IA ]