The Collaborative International Dictionary of English v.0.48:

Propagation \Prop`a*ga"tion\, n. [L. propagatio: cf. F.
   propagation.]
   [1913 Webster]
   1. The act of propagating; continuance or multiplication of
      the kind by generation or successive production; as, the
      propagation of animals or plants.
      [1913 Webster]

            There is not in nature any spontaneous generation,
            but all come by propagation.          --Ray.
      [1913 Webster]

   2. The spreading abroad, or extension, of anything;
      diffusion; dissemination; as, the propagation of sound;
      the propagation of the gospel. --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

propagation
    n 1: the spreading of something (a belief or practice) into new
         regions [syn: propagation, extension]
    2: the act of producing offspring or multiplying by such
       production [syn: generation, multiplication,
       propagation]
    3: the movement of a wave through a medium