The definition of an exurb is an area beyond the suburbs where the wealthy people live.
A wealthy area where people live outside of the suburbs of Philadelphia is an example of an exurb.
a region, generally semirural, beyond the suburbs of a city, inhabited largely by persons in the upper-income group
Origin of exurbex- + (sub)urb: coined (1955) by A. C. Spectorsky (1910-72), United States author and editor
A semirural region lying just beyond the suburbs of a city.
Origin of exurbex- (sub)urb