A prophet was someone who spoke or wrote prophecies.
In 2257 of the Mirror universe, Sarek was called "The Prophet" by the leader of the Rebellion, Voq the Fire wolf. In his position, Sarek would his mind melding abilities to see if there was peace in people's heart.(DIS: "The Wolf Inside")
In 2367, the impostor masquerading as Ardra told Acost Jared and the other Ventaxians not to "talk like some ancient prophet around me, with thees and thous and most powerful ones". (TNG: "Devil's Due")
In 2377, upon The Doctor's expression of disinterest in being worshipped by other holograms as the central focus of a new religion, Iden told him, "Prophets are chosen, Doctor. It's a blessing and a burden." (VOY: "Flesh and Blood")