A fortune teller was someone who allegedly made use of supernatural or other powers to predict future events. Generally, this was done for profit or other personal gain.
In 2371, Quark referred to Miles O'Brien as a fortune teller due to his time travels to a few hours in the future. O'Brien did not like being referred to that way, but nevertheless correctly predicted a spin on the dabo wheel shortly after. (DS9: "Visionary")