something in a film that moves the plot (= story) forward but is not important itself

Most mysteries have a MacGuffin, an event or item designed to motivate the characters but which is actually just a meaningless placeholder. 大多数悬疑片都有所谓的“麦加芬”，即为塑造角色而设计的事件或物品，但其本身不过是形式而已，没有什么意义。

Hitchcock described the "MacGuffin" as a meaningless, unimportant detail that solely existed to serve as a reason for the story to exist. 希区柯克将 "麦加芬"定义为一个毫无意义、不重要的细节，其存在完全是为了作为故事存在的理由。