Be punished or blamed for something, as in I don't want to take the rap for Mary, who forgot to mail the check in time, or Steve is such a nice guy that he's always taking the rap for his colleagues. This slangy idiom originally used rap in the sense of “a criminal charge,” a usage still current. By the mid-1900s it was also used more broadly.

To be punished or blamed, especially when innocent: “The crime boss arranged it so that his underling took the rap for the insurance scam.”