[{"Bold_text": "verb (used without object)", "List Items": ["to utter words indistinctly or in a low tone, often as if talking to oneself; murmur.", "to complain murmuringly; grumble.", "to make a low, rumbling sound."]}, {"Bold_text": "verb (used with object)", "List Items": ["to utter indistinctly or in a low tone:to mutter complaints."]}, {"Bold_text": "noun", "List Items": ["the act or utterance of a person who mutters."]}]