From Longman Dictionary of Contemporary Englishfool's goldˌfool’s ˈgold noun [uncountable] 1 HEGa kind of yellow metal that exists in some rocks and looks like gold2 DISAPPOINTEDsomething that you think will be very exciting, very attractive etc but in fact is not
Examples from the Corpus
fool's gold• Those who follow cash of the other sort were chasing fool's gold.• If one believes this, then the attraction of a fixed-rate mortgage in 1992 could easily prove fool's gold. 