Noun

• S: (n) mutter, muttering, murmur, murmuring, murmuration, mussitation (a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech)
• direct hypernym / inherited hypernym / sister term
• derivationally related form
• S: (n) murmur vowel, murmur (a schwa that is incidental to the pronunciation of a consonant)
• S: (n) heart murmur, cardiac murmur, murmur (an abnormal sound of the heart; sometimes a sign of abnormal function of the heart valves)
• S: (n) grumble, grumbling, murmur, murmuring, mutter, muttering (a complaint uttered in a low and indistinct tone)
• direct hypernym / inherited hypernym / sister term
• derivationally related form

Verb

• S: (v) murmur (speak softly or indistinctly) "She murmured softly to the baby in her arms"
• S: (v) murmur, mutter, grumble, croak, gnarl (make complaining remarks or noises under one's breath) "she grumbles when she feels overworked"