clown

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A buffoon or jester who entertains by jokes, antics, and tricks in a circus, play, or other presentation.
• noun One who jokes and plays tricks.
• noun A coarse, rude, vulgar person; a boor.
• noun A peasant; a rustic.
• intransitive verb To behave like a buffoon or jester.
• intransitive verb To perform as a buffoon or jester.
• intransitive verb To krump, especially in clown makeup.

from The Century Dictionary.

• To act or behave as a clown; play the clown.
• noun A man of rustic or coarse manners; a person without refinement; a lout; a boor; a churl.
• noun A husbandman; a peasant; a rustic.
• noun A professional or habitual jester; a merryman or buffoon, as in a pantomime, circus, or other place of entertainment, and formerly in the households of the great.
• noun Synonyms See jester and zany.

from the GNU version of the Collaborative International Dictionary of English.

• noun A man of coarse nature and manners; an awkward fellow; an ill-bred person; a boor.
• noun One who works upon the soil; a rustic; a churl.
• noun The fool or buffoon in a play, circus, etc.
• intransitive verb obsolete To act as a clown; -- with it.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A performance artist often associated with a circus and typically characterised by bright, oversized clothing, a red nose, face paint, and a brightly colored wig and who performs slapstick.
• noun A person who acts in a silly fashion.
• verb To act in a silly fashion.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb act as or like a clown
• noun a person who amuses others by ridiculous behavior
• noun a rude or vulgar fool