Available Definitions:
1) v. i. - To murmur or mutter with discontent; to make ill-natured complaints in a low voice and a surly manner.
2) v. i. - To growl; to snarl in deep tones; as, a lion grumbling over his prey.
3) v. i. - To rumble; to make a low, harsh, and heavy sound; to mutter; as, the distant thunder grumbles.
4) v. t. - To express or utter with grumbling.
5) n. - The noise of one that grumbles.
6) n. - A grumbling, discontented disposition.