The Collaborative International Dictionary of English v.0.48:

Joke \Joke\, n. [L. jocus. Cf Jeopardy, Jocular, Juggler.]
   [1913 Webster]
   1. Something said for the sake of exciting a laugh; something
      witty or sportive (commonly indicating more of hilarity or
      humor than jest); a jest; a witticism; as, to crack
      good-natured jokes.
      [1913 Webster]

            And gentle dullness ever loves a joke. --Pope.
      [1913 Webster]

            Or witty joke our airy senses moves
            To pleasant laughter.                 --Gay.
      [1913 Webster]

   2. Something not said seriously, or not actually meant;
      something done in sport.
      [1913 Webster]

            Inclose whole downs in walls, 't is all a joke.
                                                  --Pope.
      [1913 Webster]

   In joke, in jest; sportively; not meant seriously.

   Practical joke. See under Practical.
      [1913 Webster]