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.]
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   1. A deed; an action; a gest. [Obs.]
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            The jests or actions of princes.      --Sir T.
                                                  Elyot.
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   2. A mask; a pageant; an interlude. [Obs.] --Nares.
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            He promised us, in honor of our guest,
            To grace our banquet with some pompous jest. --Kyd.
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   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.
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            I must be sad . . . smile at no man's jests. --Shak.
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            The Right Honorable gentleman is indebted to his
            memory for his jests, and to his imagination for his
            facts.                                --Sheridan.
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   4. The object of laughter or sport; a laughingstock.
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            Then let me be your jest; I deserve it. --Shak.
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   In jest, for mere sport or diversion; not in truth and
      reality; not in earnest.
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            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.
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The Collaborative International Dictionary of English v.0.48:

Jest \Jest\, v. i. [imp. & p. p. Jested; p. pr. & vb. n.
   Jesting.]
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   1. To take part in a merrymaking; -- especially, to act in a
      mask or interlude. [Obs.] --Shak.
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   2. To make merriment by words or actions; to joke; to make
      light of anything.
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            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.
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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]