Fat city is a slang term that refers to a state or situation of wealth, success, or good fortune. There are several synonyms that can be used to express the same meaning, such as "easy street," "gravy train," "high life," "lap of luxury," "promised land," "El Dorado," "land of milk and honey," among others. These expressions are used to convey the idea of a life of comfort, abundance, and prosperity, often describing a situation where one can achieve their dreams and live without financial worries. Using these synonyms can add variety to the language and make the writing or conversation more engaging and entertaining.