grumble

Short definition from Wiktionary

Noun

1. 1
   A low thundering, rumbling or growling sound.
2. 2
   The sound made by a hungry stomach.
3. 3
   A surly complaint.

Verb

1. 1
   To make a low, growling or rumbling noise, like a hungry stomach or certain animals.
2. 2
   To complain; to murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.
3. 3
   To utter in a grumbling fashion.