The Collaborative International Dictionary of English v.0.48:

agitprop \agitprop\ n.
   1. [agitation + propaganda.]

   1. agitation and propaganda; -- used especially for such
      activities carried out on behalf of communist activists.
      [PJC]

   2. a person who disseminates messages calculated to assist
      some cause or some government; one disseminating
      agitprop[1]. Also called agitpropist.

   Syn: propagandist
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

agitprop
    n 1: political propaganda (especially communist propaganda)
         communicated via art and literature and cinema