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 "DS9's most famous fortune teller" following his time travels to a few hours in the future. O'Brien did not like being referred to that way, as he wasn't telling anybody their futures, and Quark assured him it was only a figure of speech. Nevertheless, he correctly predicted a spin on the dabo wheel shortly after. (DS9: "Visionary")