Definitions of fool:

• noun:   a person who lacks good judgment
• noun:   a person who is gullible and easy to take advantage of
• noun:   a professional clown employed to entertain a king or nobleman in the middle ages
• verb:   make a fool or dupe of
• verb:   indulge in horseplay

  Example: "The bored children were fooling about"

• verb:   fool or hoax

  Example: "You can't fool me!"

• verb:   spend frivolously and unwisely