Illuminati was originally the name of a real secret society founded in Bavaria (part of Germany) in the 1700s, which only lasted a short time. Today, most people use the word in a completely different, joking or conspiracy-theory way - to talk about an imaginary secret group that supposedly controls the world's governments, money, or celebrities. When someone says 'that's the Illuminati' today, they usually mean it half-jokingly, not as a real historical fact.

（歷史）光明會；（現代網路用語）陰謀論中操控世界的神秘組織（多半半開玩笑）