mutter verb
ADV. gruffly, harshly, hoarsely, huskily, thickly, through clenched/gritted teeth ‘I don't need a drink, ’ she muttered through clenched teeth. | quietly, softly, under your breath | incoherently, vaguely | angrily, bitterly, darkly, fiercely, grimly, irritably, savagely, ungraciously Helen began muttering darkly about hospitals.
VERB + MUTTER be heard to, hear sb A number of non-British visitors were heard to mutter that it would not have happened in Frankfurt. She heard him mutter an oath under his breath.
PREP. about muttering about the incompetence of the office staff | to muttering incoherently to himself
You can also check other dicts: mutter (English, 中文解释 ), wordnet sense, Collins Definition