What is the meaning of murmur?

noun

• A low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech.
  • synonyms: mutter, muttering, murmuring, murmuration, mussitation
• A schwa that is incidental to the pronunciation of a consonant.
  • synonyms: murmur vowel
• An abnormal sound of the heart; sometimes a sign of abnormal function of the heart valves.
  • synonyms: heart murmur, cardiac murmur
• A complaint uttered in a low and indistinct tone.
  • synonyms: grumble, grumbling, murmuring, mutter, muttering

verb

• Speak softly or indistinctly.
  • usage: "She murmured softly to the baby in her arms"
• Make complaining remarks or noises under one's breath.
  • usage: "she grumbles when she feels overworked"
  • synonyms: mutter, grumble, croak, gnarl