Chicago lightning

A vivid, dated American slang term for bullets or gunfire — coined during the Prohibition era when Chicago became synonymous with gang warfare, tommy guns, and mob violence. The phrase captures the sudden, deadly speed of gunfire by likening it to a lightning strike, while rooting it geographically in the city that became the symbol of organized crime in the 1920s and 30s. You'll find it in crime fiction, old movies, and historical accounts of that period.