A clown is someone who makes people laugh, like the guy with the red nose and oversize polka dotted tie. It can also be an insult — a rude buffoon can be called a clown. To clown means to act goofy.
The clowns found at circuses and birthday parties usually wear makeup and big shoes, but funny people in regular clothes are often called clowns, too, as in the class clown who tells jokes in school. Also, someone obnoxious can be called a clown, as in “that clown wrecked my car!” Acting like a clown in any way is clowning. A teacher trying to get the attention of kids who are fooling around might say, "Stop clowning around!”