Flash in the pan is an idiomatic expression that describes a short-lived success or a temporary phenomenon that fails to last. The term originally referred to a flintlock firearm that ignited its priming powder but failed to fire the main charge, making a flash in the pan but no gunfire. There are numerous synonyms for "flash in the pan" which includes transient, temporary, short-lived, brief, momentary, passing, ephemeral, and fleeting. These synonyms are used to describe something that doesn't last or isn't permanent, such as a novelty or a fad, and many could be used interchangeably with "flash in the pan" depending on the context.