Court conjurer, or also King's conjurer, was the title given to the conjurer assigned to the court of Stormwind Keep. The court conjurer was not some simple jester and was expected to advise the throne of Wrynn on the matters of magic.
In the decades prior to the First War, Nielas Aran was the court conjurer of King Barathen Wrynn. His son Medivh himself was expected to be given the title of Apprentice Conjurer to the Court after attaining the Age of Ascension.
The non-canon human ending to Warcraft I mentions the people of the kingdom being delighted by a display of mystic sights and sounds provided by the court conjurers while being treated to a feast of unequaled splendor.