A Definition to Start With . . .

There are many ways to define the term "propaganda."    Here is a good one to begin with from a standard text on the subject:

“Propaganda is a form of communication that attempts to achieve a response that furthers the desired intent of the propagandist. Persuasion is interactive and attempts to satisfy the needs of both the persuader and the persuadee. A model of propaganda depicts how elements of informative and persuasive communication may be incorporated into propagandistic communication, thus distinguishing propaganda as a specific class of communication . . . . Public opinion and behavioral change can be affected by propaganda.”  [Jowett & O'Donnell, Propaganda & Mass Persuasion, p.1]

A more concise definition from the same source:

“Propaganda is the deliberate, systematic attempt to shape perceptions, manipulate cognitions, and direct behavior to achieve a response that furthers the desired intent of the propagandist.” [Jowett & O'Donnell, p.6.]