The Collaborative International Dictionary of English v.0.48:

Propaganda \Prop`a*gan"da\, n. [Abbrev. fr. L. de propaganda
   fide: cf. F. propagande. See Propagate.]
   [1913 Webster]
   1. (R. C. Ch.)
      (a) A congregation of cardinals, established in 1622,
          charged with the management of missions.
      (b) The college of the Propaganda, instituted by Urban
          VIII. (1623-1644) to educate priests for missions in
          all parts of the world.
          [1913 Webster]

   2. Hence, any organization or plan for spreading a particular
      doctrine or a system of principles.
      [1913 Webster]

WordNet (r) 3.0 (2006):

propaganda
    n 1: information that is spread for the purpose of promoting
         some cause