<p><strong>Verb (used without object):</strong></p><ul><li>to murmur or mutter in discontent; complain sullenly: Tim always found something to grumble about.</li><li>to utter low, indistinct sounds; growl: Suddenly I heard my stomach grumble, and realized I hadn't had any lunch.</li><li>to rumble: The thunder grumbled in the west.</li></ul><p><strong>Verb (used with object):</strong></p><ul><li>to express or utter with murmuring or complaining.</li></ul><p><strong>Noun:</strong></p><ul><li>an expression of discontent; complaint; unhappy murmur; growl.</li><li>grumbles, a grumbling, discontented mood.</li><li>a rumble.</li></ul>