/ ˌpɪkədɪli ˈsɜːkəs; NAmE ˈsɜːrkəs/ noun
( BrE ) used to describe a place that is very busy or crowded :
It's been like Piccadilly Circus in this house all morning.
ORIGIN: From the name of a busy area in the centre of London where several large roads meet and where there is always a lot of traffic.
—compare Grand Central Station
For more information see the Cultural Guide