growl vs grumble

growl and grumble both are nouns.

Word	Noun	Adjective	Verb	Adverb
growl	Yes	No	Yes	No
grumble	Yes	No	Yes	No

As verbs, growl and grumble are synonyms defined as:

Other synonyms of growl include rumble.

growl (noun)	grumble (noun)
the sound of growling (as made by animals)	a complaint uttered in a low and indistinct tone
	a loud low dull continuous noise

growl (verb)	grumble (verb)
to utter or emit low dull rumbling sounds	make complaining remarks or noises under one's breath
	show one's unhappiness or critical attitude
	to utter or emit low dull rumbling sounds
	make a low noise