(covers information from several alternate timelines)
An orator, public speaker, or simply speaker, was a person who delivered speeches.
The Chancellor Kultarey, the speaker at the political rally that was covertly attended by the landing party from Enterprise NX-01 in 2152, was said to have reminded Malcolm Reed of Winston Churchill before World War II. (ENT: "The Communicator")
In 2258 of the alternate reality, James T. Kirk dismissed Spock's assertion that he was not cleared to be aboard USS Enterprise, saying, "Look, I get it, you're a great orator. I'd love to do it again with you too." This was in reference to their earlier verbal sparring session at Kirk's hearing before the Starfleet Academy Board regarding the cadet's cheating on the Kobayashi Maru scenario. (Star Trek)
In 2370, while trying to sell desiccated discs of the Ferengi businessman Plegg, Quark expressed his belief that it would require an orator with the deceased's skills to praise him. (DS9: "The Alternate")