Propaganda, n. 1. any organization or movement working for the propagation of particular ideas, doctrines, practices, etc. 2. the ideas, doctrines, practices, etc. spread in this way. (Webster’s New Twentieth Century Dictionary)
Propaganda: 3. a storyforming/storytelling technique used to impact an audience in specific ways, often employed to instigate deliberation and/or action. (Dramatica)
Propaganda is a wondrous and dangerous story device. Its primary usage in stories is as a method for an author to impact an audience long after they have experienced the story itself. Through the use of propaganda, an author can inspire an audience to think certain ways, think about certain things, behave certain ways, and take specific actions. Like fire and firearms, propaganda can be used constructively and destructively and does not contain an inherent morality. Any morality involved comes from the minds of the author and his audience.
From the Dramatica Theory Book