Definition of Bonanza

Noun: bonanza bu'nan-zu

A sudden happening that brings good fortune (as a sudden opportunity to make money)
"the demand for testing has created a bonanza for those unregulated laboratories where boxes of specimen jars are processed like an assembly line";
- boom, gold rush, gravy, godsend, manna from heaven, windfall, bunce [Brit]
An especially rich vein of precious ore