An expression of disbelief or incredulity. (Sometimes used ironically or disingenuously.) The phrase comes from the catchphrase from the Irish game show Quicksilver. Primarily heard in Ireland. A: "My aunt Edna won the lotto!" B: "Stop the lights, that's incredible news!" A: "My uncle Pat once met President Reagan, you know." B: "Ah here, stop the lights. Your uncle Pat's never even been to America!" Stop the lights, Jimmy's buying a round for everyone! I never thought I'd see the day!