comedian

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

• noun A professional entertainer who tells jokes or performs various other comic acts.
• noun An actor in comedy.
• noun A writer of comedy.
• noun A person who amuses or tries to be amusing; a clown.

from The Century Dictionary.

• noun One who acts or plays parts in a comic drama, whether male or female.
• noun An actor or player generally.
• noun A writer of comedy; a comic dramatist.

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

• noun An actor or player in comedy.
• noun A writer of comedy.

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

• noun An entertainer who performs in a humorous manner, especially by telling jokes.
• noun by extension Any person who is characteristically humorous or amusing.
• noun A writer of comedy.

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

• noun an actor in a comedy
• noun a professional performer who tells jokes and performs comical acts