rumbling noun 2adjective 1forms 3 noun2 •A deep low noise.The rumbling of distant thunder echoed from the hilltop. •A muted sound of complaint or discontent (often used in the plural).The rumblings of the masses precede the crumbling of the state. adjective1 •Deep- and slow-sounding.His rumbling voice suited the solemn occasion.rumbling stomachs formsrumblings · more rumbling · most rumbling