grum·ble 
(grŭmbəl)
(grŭmbəl)v. grum·bled, grum·bling, grum·bles
v.intr.
1. To complain in a surly manner; mutter discontentedly: "The governed will always find something to grumble about" (Crane Brinton).
2. To rumble or growl.
v.tr.
To express in a grumbling discontented manner: grumbled a rude response.
n.
1. A muttered complaint.
2. A rumble; a growl.
[Probably Dutch grommelen, to mutter, from Middle Dutch, frequentative of grommen.]
grumbler n.
grumbling·ly adv.
grumbly adj.