April Fools' Day
April Fools' Day 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.
April 1; All Fools' Day, when practical jokes are played on the unsuspecting
April Fools' Day definition by American Heritage Dictionary
April 1, celebrated in various countries, including the United States and Great Britain, and marked by the playing of practical jokes. Also called All Fools' Day.