Answer: mutters

AnswerCrossword Clue
MUTTERSGrumbles quietly
MUTTERSIndistinct utterances.
MUTTERSGrumbles.
MUTTERSGrumbles, sotto voce.
MUTTERSGrowls
MUTTERSSpeaks indistinctly
MUTTERSComplains
MUTTERSComplains sotto voce
MUTTERSSays "You no-good son of a ...," say
muttersthe act or sound of muttering
muttersto speak low and indistinctly; grumble
muttersMUTTER, to murmur (to make a subdued muttered sound)