A fool's cap.
fool's cap definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a cap, usually with bells, formerly worn by a court fool or jester
fool's cap definition by American Heritage Dictionary
- A gaily decorated cap, usually with a number of loose peaks tipped with bells, formerly worn by court jesters and clowns.
- See dunce cap.