n. The act of propagating; the multiplication or continuance of the kind or species by natural generation or reproduction: as, the propagation of plants or animals.n. The spreading or extension of anything; diffusion: as, the propagation of Christianity; the propagation of socialistic ideas.n. Increase; augmentation; enlargement; aggrandizement.n. Transmission from one point to another, as of sound by waves of condensation and rarefaction in the air, and of radiant heat and light by undulations in the ether. See sound, heat, light, and radiant energy (under energy).n. Synonyms Increase, generation, procreation, breeding.n. Dissemination.