From Longman Dictionary of Contemporary Englishupper crustˌupper ˈcrust noun [singular] informalCLASS IN SOCIETY the group of people who belong to the highest social class —upper-crust adjective
Examples from the Corpus
upper crust• In fact there were complaints from upper crust visitors about the din, so the cells fell into disuse.• Only society's upper crust would have traveled in the car, known as the limousine of its day.• Those disgraceful students were males from the upper crust.• In Harehills I belonged to the upper crust of the lower middle classes who were getting out as fast as they could.• The upper crust does not ride public transportation. 