Толковый словарь английского языка Oxford English Reference - grumble

v. & n. --v. 1 intr. a (often foll. by at, about, over) complain peevishly. b be discontented. 2 intr. a utter a dull inarticulate sound; murmur, growl faintly. b rumble. 3 tr. (often foll. by out) utter complainingly. 4 intr. (as grumbling adj.) colloq. giving intermittent discomfort without causing illness (a grumbling appendix). --n. 1 a complaint. 2 a a dull inarticulate sound; a murmur. b a rumble. Derivatives grumbler n. grumbling adj. grumblingly adv. grumbly adj. Etymology: obs. grumme: cf. MDu. grommen, MLG grommelen, f. Gmc