grumble vs rumble

grumble and rumble both are nouns.

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

As nouns, grumble and rumble are synonyms defined as:

Other synonyms of grumble include grumbling, rumbling.

As verbs, grumble and rumble are synonyms defined as:

Other synonyms of grumble include growl.

As verbs, grumble and rumble are synonyms defined as:

grumble (noun)	rumble (noun)
a complaint uttered in a low and indistinct tone	a fight between rival gangs of adolescents
a loud low dull continuous noise	a servant's seat (or luggage compartment) in the rear of a carriage
	a loud low dull continuous noise

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