Flash mob

A flash mob (or flashmob) is when people suddenly come together in a public place to do something. After they are done, they disperse again. Many times, the people coming together do not know each other. Flash mobs are often done for entertainment, satire, and art. Flash mobs may be organized via telecommunications, social media, or viral emails.
The term was first used in 2003. It is generally not used for events and performances organized for politics (such as protests), advertisments, or actions that involve public relation firms or paid professionals. If a flash mob is planned, the term smart mob is often used.
The term "flash rob" or "flash mob robberies", a reference to the way flash mobs assemble, has been used to describe many robberies and assaults done by groups of teenage youth. Bill Wasik, originator of the first flash mobs, and a number of other commentators have questioned or objected to the usage of "flash mob" to describe criminal acts. Flash mob has also been featured in some Hollywood movie series, such as "Step Up".