What is the meaning of Grumble?

A low thundering, rumbling or growling sound.

The sound made by a hungry stomach.

A surly complaint.

To make a low, growling or rumbling noise, like a hungry stomach or certain animals.

To complain; to murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.

To utter in a grumbling fashion.

Source: wiktionary.org