Grumbling
verb
To make a low, growling or rumbling noise, like a hungry stomach or certain animals.
“The distant thunder grumbles.”
To complain; to murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.
“He grumbles about the food constantly, but has yet to learn to cook.”
To utter in a grumbling fashion.
noun
Complaining
“the grumblings of a bad-tempered man”
Rumbling