grumbling
verb
Definitions
To make a low, growling or rumbling noise, like a hungry stomach or certain animals.
Example: 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.
Example: He grumbles about the food constantly, but has yet to learn to cook.
To utter in a grumbling fashion.
noun
Definitions
Complaining
Example: the grumblings of a bad-tempered man
Rumbling