WordNet (r) 3.0 (2006):

gold rush
    n 1: a sudden happening that brings good fortune (as a sudden
         opportunity to make money); "the demand for testing has
         created a boom for those unregulated laboratories where
         boxes of specimen jars are processed like an assembly line"
         [syn: boom, bonanza, gold rush, gravy, godsend,
         manna from heaven, windfall, bunce]
    2: a large migration of people to a newly discovered gold field