The Collaborative International Dictionary of English v.0.48:

Jest \Jest\ (j[e^]st), n. [OE. jeste, geste, deed, action,
   story, tale, OF. geste, LL. gesta, orig., exploits, neut. pl.
   from L. gestus, p. p. of gerere to bear, carry, accomplish,
   perform; perh. orig., to make to come, bring, and perh. akin
   to E. come. Cf. Gest a deed, Register, n.]
   [1913 Webster]
   1. A deed; an action; a gest. [Obs.]
      [1913 Webster]

            The jests or actions of princes.      --Sir T.
                                                  Elyot.
      [1913 Webster]

   2. A mask; a pageant; an interlude. [Obs.] --Nares.
      [1913 Webster]

            He promised us, in honor of our guest,
            To grace our banquet with some pompous jest. --Kyd.
      [1913 Webster]

   3. Something done or said in order to amuse; a joke; a
      witticism; a jocose or sportive remark or phrase. See
      Synonyms under Jest, v. i.
      [1913 Webster]

            I must be sad . . . smile at no man's jests. --Shak.
      [1913 Webster]

            The Right Honorable gentleman is indebted to his
            memory for his jests, and to his imagination for his
            facts.                                --Sheridan.
      [1913 Webster]

   4. The object of laughter or sport; a laughingstock.
      [1913 Webster]

            Then let me be your jest; I deserve it. --Shak.
      [1913 Webster]

   In jest, for mere sport or diversion; not in truth and
      reality; not in earnest.
      [1913 Webster]

            And given in earnest what I begged in jest. --Shak.

   Jest book, a book containing a collection of jests, jokes,
      and amusing anecdotes; a Joe Miller.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jest \Jest\, v. i. [imp. & p. p. Jested; p. pr. & vb. n.
   Jesting.]
   [1913 Webster]
   1. To take part in a merrymaking; -- especially, to act in a
      mask or interlude. [Obs.] --Shak.
      [1913 Webster]

   2. To make merriment by words or actions; to joke; to make
      light of anything.
      [1913 Webster]

            He jests at scars that never felt a wound. --Shak.

   Syn: To joke; sport; rally.

   Usage: To Jest, Joke. One jests in order to make others
          laugh; one jokes to please himself. A jest is usually
          at the expense of another, and is often ill-natured; a
          joke is a sportive sally designed to promote good
          humor without wounding the feelings of its object.
          "Jests are, therefore, seldom harmless; jokes
          frequently allowable. The most serious subject may be
          degraded by being turned into a jest." --Crabb.
          [1913 Webster]

WordNet (r) 3.0 (2006):

jest
    n 1: a humorous anecdote or remark intended to provoke laughter;
         "he told a very funny joke"; "he knows a million gags";
         "thanks for the laugh"; "he laughed unpleasantly at his own
         jest"; "even a schoolboy's jape is supposed to have some
         ascertainable point" [syn: joke, gag, laugh, jest,
         jape]
    2: activity characterized by good humor [syn: jest, joke,
       jocularity]
    v 1: tell a joke; speak humorously; "He often jokes even when he
         appears serious" [syn: joke, jest]
    2: act in a funny or teasing way [syn: joke, jest]

Moby Thesaurus II by Grady Ward, 1.0:

189 Moby Thesaurus words for "jest":
   Parthian shot, a continental, a curse, a damn, a darn, a hoot,
   back answer, badinage, bagatelle, banter, bauble, be merry with,
   bean, belly laugh, bibelot, bit, blue story, brass farthing, butt,
   button, byword, byword of reproach, caustic remark, cent, chaff,
   comeback, crack, crack a joke, crack wise, curio, cut,
   cutting remark, derision, dig, dirty joke, dirty story,
   double entendre, drollery, dump, dupe, ethnic joke, exchange,
   fair game, farce, farthing, feather, fig, figure of fun, fleabite,
   fleer, fleer at, flout, folderol, fool, foolery, fooling,
   fooling around, fribble, frippery, fun, funny story, gag, game,
   gaud, gazingstock, gewgaw, gibe, gibe at, gibing retort, gimcrack,
   gird, give-and-take, goat, good one, good story,
   good-natured banter, hair, halfpenny, harmless teasing, haze,
   hill of beans, howler, jab, jape, jeer, jestbook, jestingstock,
   jive, joke, jolly, josh, kickshaw, kid, kid around, kidding,
   kidding around, knickknack, knickknackery, laugh, laughingstock,
   leg-pull, make a funny, make fun, make fun of, minikin, mock,
   mockery, molehill, monkey, needle, panic, parting shot, peppercorn,
   persiflage, picayune, pilgarlic, pin, pinch of snuff, pinprick,
   play, play on words, pleasantry, point, poke fun at, pun, put on,
   put-down, put-on, quip, rag, raillery, rally, rallying, rap, razz,
   red cent, rib, rib tickler, ride, ridicule, riot, roast,
   row of pins, rude reproach, rush, scintillate, scoff, scoff at,
   scream, scurrility, shit, short answer, sick joke, sidesplitter,
   sight gag, slam, slap, snap, sneeshing, sou, sparkle, sport, stock,
   story, straw, swipe, target, taunt, tease, toy, trifle, trinket,
   triviality, tuppence, twit, two cents, twopence, utter a mot,
   verbal thrust, victim, visual joke, waggery, wheeze, whim-wham,
   wisecrack, witticism, wow, yak, yarn