Definition from Wiktionary, the free dictionary
buffoon (plural buffoons)
- One who acts in a silly or ridiculous fashion; a clown or fool.
- (pejorative) An unintentionally ridiculous person.
Usage notes 
- In the United States the term is used most commonly to describe inappropriate, clownish figures on the public stage; here the behavior of a variety of public figures have caused them to be described as buffoons by their political opponents.
- In the UK the term is used more broadly, to describe such people who are held in popular regard but who nevertheless engender amusement with their pronouncements and acts.
Derived terms 
one who acts in a silly or ridiculous fashion