A bozo is a goofy, ridiculous person. A frustrated preschool teacher might beg her students to sit down and stop acting like bozos.
You can use the informal term bozo to describe someone who's harmlessly goofy, or alternately, someone who is annoyingly rude. If your candidate for President loses, you might say: "How could all those bozos vote for that guy?" While the exact origin of bozo is unknown, the word became strongly associated with foolishness thanks to the popular TV clown named Bozo who entertained American children from about 1950 until 2001.