The word "kerflooey" is an informal term that means something has gone wrong or has stopped working unexpectedly. There are several other synonyms for this word, including "kaput," "busted," "broken," "malfunctioning," "out of order," "defunct," and "non-functional." These synonyms can be used interchangeably depending on the context and tone of the situation. For instance, you may use "kaput" or "busted" to describe a machine that has stopped working, while "defunct" or "non-functional" is more appropriate when referring to a company that has closed down. Ultimately, choosing the right synonym depends on the intended meaning and the audience.