The act of leading the thinking of a significant group of other people in the context of business, politics and media. Not necessarily an original or innovative thinker. Ideally, a thought leader presides over one or more public platforms from which to disseminate point of views and thereby influence the thinking, vocabulary, and business strategies of a market. Ideally, thought leaders influence both buyers and sellers in a given industry/sector/market.
Also see pundit, which you can think of as a credentialed thought leader, often tied to one or more institutions.