mass hysteria

n. collective hysteria, uncontrollable outburst of emotion exhibited by a mass of people, exaggerated emotional response affecting a group of persons

Mass hysteria, also called collective hysteria or collective obsessional behavior, is the sociopsychological phenomenon of the manifestation of the same or similar hysterical symptoms by more than one person. A common manifestation of mass hysteria occurs when people believe they are suffering from a similar disease or ailment.
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Mass hysteria n. 1. Spontaneous, en masse development of identical physical or emotional symptoms among a group of individuals, as in a classroom of [more]Mass hysteria - Community and Resources

Noun
1. a condition in which a large group of people exhibit the same state of violent mental agitation
(synonym) epidemic hysertia
(hypernym) craze, delirium, frenzy, fury, hysteria

Irrational or wild behavior that spreads rapidly through a crowd or through a section of a society.