Definitions of fun:

• noun:   activities that are enjoyable or amusing

  Example: "I do it for the fun of it"

• noun:   violent and excited activity

  Example: "She asked for money and then the fun began"

• noun:   verbal wit (often at another's expense but not to be taken seriously)

  Example: "He became a figure of fun"

• noun:   a disposition to find (or make) causes for amusement

  Example: "He was fun to be with"