"Fat-city" refers to a state of great financial prosperity or success. Some synonyms for this term include boomtown, gravy train, wealth hub, prosperous haven, or affluent metropolis. These words all suggest a place where opportunities abound, and fortunes can be made quickly. Boomtown paints a picture of a place where development and growth are occurring rapidly, while gravy train implies an easy path to financial success. Wealth hub and prosperous haven suggest a place where wealth is concentrated, and opportunities are abundant. Finally, affluent metropolis conjures up images of a cosmopolitan city where resources and money are plentiful. Each of these synonyms represents a location where financial success is attainable for those who seek it.