mumbling vs chew

mumbling and chew both are nouns.

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

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

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

Other hypernyms of mumbling include chewing, manduction, mastication.

mumbling (noun)	chew (noun)
ineffectual chewing (as if without teeth)	biting and grinding food in your mouth so it becomes soft enough to swallow
indistinct enunciation	a wad of something chewable as tobacco

mumbling (verb)	chew (verb)
	chew (food); to bite and grind with the teeth