gnarl vs grumble

gnarl and grumble both are nouns.

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

As verbs, gnarl and grumble are synonyms defined as:

gnarl and grumble: make complaining remarks or noises under one's breath

Other synonyms of gnarl include croak, murmur, mutter.

gnarl (noun)	grumble (noun)
something twisted and tight and swollen	a complaint uttered in a low and indistinct tone
	a loud low dull continuous noise

gnarl (verb)	grumble (verb)
make complaining remarks or noises under one's breath	make complaining remarks or noises under one's breath
twist into a state of deformity	show one's unhappiness or critical attitude
	to utter or emit low dull rumbling sounds
	make a low noise