A magician was someone who purported to make use of magic, either for the entertainment of others or for their own amusement.
Harry Houdini was a famous magician from Earth. According to Jonathan Archer, he could escape from virtually any restraint, an ability he thought would have been useful when he and T'Pol were captured by Coridan dissidents in 2151. (ENT: "Shadows of P'Jem")
Dr. Leonard McCoy claimed that he was "not a magician" when asked by Spock to treat his sensitivity to cold in 2267. McCoy had been thus far unable to determine a method of treatment for the accelerated aging he and other crew members were suffering from. (TOS: "The Deadly Years")
In 2367, Doctor Beverly Crusher noted that the way the impostor styling herself as Ardra delivered events such as the illusion of transforming into Fek'lhr made her seem like a magician. When Counselor Deanna Troi noted that "Ardra" had an especially focused mind that was nearly impossible for her to read, Lieutenant commander Geordi La Forge noted that "The best magicians will never let you see what's up their sleeve." (TNG: "Devil's Due")