Answer: grumble

AnswerCrossword Clue
GRUMBLEMutter
GRUMBLEComplain under one's breath
GRUMBLEComplain.
GRUMBLEComplain
GRUMBLEGROUSE
GRUMBLEGrouse
GRUMBLEMutter complaints
grumbleto mutter in discontent
grumbleto mutter in discontent
grumbleexpress with grumbling
grumbleowl rumble