grumbles is a form of:

Grumble



noun
1.
(a gnimbling, to mutter complaints, badtempered complaining) ការរអ៊ូរទាំ, ការរអ៊ូរទាំ
verbpast tense: grunbled ; past participle: grunbled ; present participle: grumbling ;
1.
(INTRANSITIVE) (To mutter or complain in a surly way, to growl or rumble) ទន្ទេញ, រអ៊ូរទាំ, រអ៊ូរទាំ
Example: Some children grumble about everything they have to do, agrumble of discontent.
ENGLISH MEANING
noun
1.
The noise of one that grumbles.
2.
A grumbling, discontented disposition.
verbpast tense: grunbled ; past participle: grunbled ; present participle: grumbling ;
1.
(INTRANSITIVE) To murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.
2.
(INTRANSITIVE) To growl; to snarl in deep tones; as, a lion grumbling over his prey.
3.
(INTRANSITIVE) To rumble; to make a low, harsh, and heavy sound; to mutter; as, the distant thunder grumbles.
4.
(TRANSITIVE) To express or utter with grumbling.