mumbling vs mastication

mumbling and mastication both are nouns.

Word	Noun	Adjective	Verb	Adverb
mumbling	Yes	No	No	No
mastication	Yes	No	No	No

As nouns, mastication is a hypernym of mumbling; that is, mastication is a word with a broader meaning than mumbling:

mumbling: ineffectual chewing (as if without teeth)
mastication: biting and grinding food in your mouth so it becomes soft enough to swallow

Other hypernyms of mumbling include chew, chewing, manduction.

mumbling (noun)	mastication (noun)
ineffectual chewing (as if without teeth)	biting and grinding food in your mouth so it becomes soft enough to swallow
indistinct enunciation