Synonyms of muttering

1 Syllable
growl, faint, snarl, grunt, croak, grouch, moan, groan
2 Syllables
faintest, sputter, muddle, babbled, complain, swallow, fainter, rumble, murmurs, grouse, murmur, whisper
3 Syllables
susurrus
4 Syllables
murmuration, susurration, jabberwocky