murmur - noun

a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech

a schwa that is incidental to the pronunciation of a consonant

an abnormal sound of the heart; sometimes a sign of abnormal function of the heart valves

a complaint uttered in a low and indistinct tone

murmur - verb

• speak softly or indistinctly
• make complaining remarks or noises under one's breath

murmur - thesaurus

croak   gnarl   grumble   grumbling   murmuration   murmuring   mussitation   mutter   muttering