grumble vs gnarl

grumble and gnarl both are nouns.

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

As verbs, grumble and gnarl are synonyms defined as:

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

Other synonyms of grumble include croak, murmur, mutter.

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

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