Main entry: grumble, grumbling, murmur, murmuring, mutter, muttering
Definition: a complaint uttered in a low and indistinct tone
Main entry: rumble, rumbling, grumble, grumbling
Definition: a loud low dull continuous noise
Usage: they heard the rumbling of thunder
Main entry: rumbling, grumbling
Definition: continuous full and low-pitched throbbing sound
Usage: the rumbling rolling sound of thunder