The word "improsperous" means lacking financial success or failing to thrive. There are several synonyms for this word that convey a similar meaning, including "impecunious," "impoverished," "destitute," "penniless," and "indigent." Other related terms include "down-and-out," "needy," "poor," and "strapped for cash." These words all depict a sense of financial struggle or difficulty and can be used interchangeably with "improsperous" to describe someone's financial situation or the state of a business or economy. While these words may have negative connotations, they are useful for expressing the reality of financial challenges that many people face.