flash mobbing
noun/ˈflæʃmɒbɪŋ/
/ˈflæʃmɑːbɪŋ/
[uncountable]- an activity in which a large group of people arrange (by mobile phone or email) to gather together in a public place at exactly the same time, spend a short time doing something there and then quickly all leave at the same timeTopics Phones, email and the internetc2
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flash mobbing