propagation vs spreading

propagation and spreading both are nouns.

Word	Noun	Adjective	Verb	Adverb
propagation	Yes	No	No	No
spreading	Yes	No	No	No

As nouns, spreading is a hypernym of propagation; that is, spreading is a word with a broader meaning than propagation:

propagation: the spreading of something (a belief or practice) into new regions
spreading: the opening of a subject to widespread discussion and debate

Other hypernyms of propagation include airing, dissemination, public exposure.

propagation (noun)	spreading (noun)
the act of producing offspring or multiplying by such production	act of extending over a wider scope or expanse of space or time
the spreading of something (a belief or practice) into new regions	the opening of a subject to widespread discussion and debate
the movement of a wave through a medium	process or result of distributing or extending over a wide expanse of space