murmurous vs murmur

murmurous is not a noun while murmur is a noun.

Word	Noun	Adjective	Verb	Adverb
murmurous	No	Yes	No	No
murmur	Yes	No	Yes	No

murmurous (noun)	murmur (noun)
	a complaint uttered in a low and indistinct tone
	a schwa that is incidental to the pronunciation of a consonant
	a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech
	an abnormal sound of the heart; sometimes a sign of abnormal function of the heart valves

murmurous (adjective)	murmur (adjective)
characterized by soft sounds

murmurous (verb)	murmur (verb)
	speak softly or indistinctly
	make complaining remarks or noises under one's breath