grumble
grum-ble
verb
To complain in a low, bad-tempered voice about something trivial.
"He often grumbles about the weather."
noun
A quiet, bad-tempered complaint about something, often minor.
"There were a few grumbles about the food."
Thesaurus
Synonyms: murmuring, grumbling, murmur, mutter, muttering, growl, rumble, rumbling, scold, grouch, croak, gnarl