噜 rarely stands alone in modern Chinese. You'll most often encounter it as the second syllable of onomatopoeic compounds like 呼噜 (hū lu, snoring sound) and 咕噜 (gū lu, rumbling or gurgling sound). In some dialects, 噜苏 (lū su) is used for 'verbose' or 'garrulous' (equivalent to 啰嗦). The English glosses 'grumble' and 'chatter' are rough approximations and should not be taken as direct equivalents of 噜 by itself.