The Collaborative International Dictionary of English v.0.48:

Jester \Jest"er\, n. [Cf. Gestour.]
   1. A buffoon; a merry-andrew; a court fool.
      [1913 Webster]

            This . . . was Yorick's skull, the king's jester.
                                                  --Shak.
      [1913 Webster]

            Dressed in the motley garb that jesters wear.
                                                  --Longfellow.
      [1913 Webster]

   2. A person addicted to jesting, or to indulgence in light
      and amusing talk.
      [1913 Webster]

            He ambled up and down
            With shallow jesters.                 --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

jester
    n 1: a professional clown employed to entertain a king or
         nobleman in the Middle Ages [syn: jester, fool, motley
         fool]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "jester":
   Columbine, Hanswurst, Harlequin, Pantalone, Pantaloon,
   Polichinelle, Pulcinella, Punch, Punchinello, Scaramouch, banana,
   buffo, buffoon, burlesquer, caricaturist, clown, comedian, comic,
   cutup, droll, epigrammatist, fool, funnyman, gag writer, gagman,
   gagster, harlequin, humorist, idiot, ironist, jack-pudding, joker,
   jokesmith, jokester, lampooner, madcap, merry-andrew, motley,
   motley fool, parodist, pickle-herring, prankster, punner, punster,
   quipster, reparteeist, satirist, wag, wagwit, wisecracker, wit,
   witling, zany



The Devil's Dictionary (1881-1906):

JESTER, n.  An officer formerly attached to a king's household, whose
business it was to amuse the court by ludicrous actions and
utterances, the absurdity being attested by his motley costume.  The
king himself being attired with dignity, it took the world some
centuries to discover that his own conduct and decrees were
sufficiently ridiculous for the amusement not only of his court but of
all mankind.  The jester was commonly called a fool, but the poets and
romancers have ever delighted to represent him as a singularly wise
and witty person.  In the circus of to-day the melancholy ghost of the
court fool effects the dejection of humbler audiences with the same
jests wherewith in life he gloomed the marble hall, panged the
patrician sense of humor and tapped the tank of royal tears.

    The widow-queen of Portugal
        Had an audacious jester
    Who entered the confessional
        Disguised, and there confessed her.

    "Father," she said, "thine ear bend down --
        My sins are more than scarlet:
    I love my fool -- blaspheming clown,
        And common, base-born varlet."

    "Daughter," the mimic priest replied,
        "That sin, indeed, is awful:
    The church's pardon is denied
        To love that is unlawful.

    "But since thy stubborn heart will be
        For him forever pleading,
    Thou'dst better make him, by decree,
        A man of birth and breeding."

    She made the fool a duke, in hope
        With Heaven's taboo to palter;
    Then told a priest, who told the Pope,
        Who damned her from the altar!
                                                            Barel Dort