From Longman Dictionary of Contemporary Englishbe the butt of somethingbe the butt of somethingMAKE FUN OFto be the person or thing that other people often make jokes about Paul quickly became the butt of everyone’s jokes. → butt
Examples from the Corpus
be the butt of something• Unfortunately for Ted, he's become the butt of jokes around the office.• He never dreamed he would be the butt of such a classic, almost vaudevillian joke.• At the time, you were the butt of some very unkind jokes? 