flash crowd
Noun
Meaning
Alternative form of flashcrowd
A large audience for a sporting event that is unexpected because of large numbers of game-day ticket sales rather than advance tickets.
A crowd that forms suddenly.
Alternative form of flash mob
(obsolete) The fashionable public.
Source: en.wiktionary.orgExamples
Other reading *"Flash Crowd" is included in the short story collection The Flight of the Horse.