v (intransitive|now|_|rare) To grumble; to complain in a low, muttering voice, or express discontent (term|at) or (term|against) someone or something. (defdate|from 14th c.)
v (intransitive) To speak or make low, indistinguishable noise; to mumble, mutter. (defdate|from 14th c.)
v (transitive) To say (something) indistinctly, to mutter. (defdate|from 15th c.)