grumbling >> ˈɡrʌmblɪŋ
Definition: [noun] the action or fact of complaining in a bad-tempered way.
Example: despite his grumbling, he tried to exercise every day
Definition: [adjective] expressing a complaint in a bad-tempered way.
Example: grumbling employees said they were prevented from accessing e-commerce sites
Definition: [adjective] making a low rumbling sound.
Example: you don't have to sacrifice your diet to silence a grumbling stomach