To make a low rumbling sound; mutter; growl.To complain in a low, surly voice; murmur with discontent.Synonyms To complain, repine, croak.To express or utter in a grumbling or complaining manner.n. The act of grumbling; a grumbling speech or remark.n. A surly person.n. plural A grumbling, discontented mood; a fit of the spleen.