A spokesman was an individual who made statements for another or for a group.
In 2268, Lieutenant Nyota Uhura monitored the radio waves of the planet 892-IV. She heard the Roman Empire spokesman disparaging the religion of the Children of the Sun. However, he could not disparage the religion, for the Children were not worshipping the sun. They were worshipping the Son of God. (TOS: "Bread and Circuses")
In 2367, in an illusory future created by Barash, William T. Riker was the key spokesman in securing an alliance between the Federation and the Romulan Star Empire. Riker had gained the trust of the Romulans after years of distrust and conflict by saving the crew of a Romulan battle cruiser. (TNG: "Future Imperfect")
In 2370, Quark was the spokesman for the Promenade Merchants' Association. When the Promenade was closed for longer than usual, Quark said he was going to file a official protest with Captain Benjamin Sisko. Sisko informed him to put in writing. Quark left to get a PADD. (DS9: "Treachery, Faith and the Great River")