A pep talk was a speech intended to lift the morale of its audience.
In 2273, Will Decker, upon the sudden appearance of Admiral James T. Kirk on the bridge of the USS Enterprise, Will Decker expressed his hope that Kirk hadn't come to give him a Starfleet pep talk, as he was far too preoccupied to listen. (Star Trek: The Motion Picture)
In 2376, when Seven of Nine suggested to Neelix that he might be unable to reach a logicless Tuvok, the Talaxian sarcastically thanked her for the pep talk. (VOY: "Riddles")