Lewis & Short

mūtĭo or muttĭo, īvi, 4, v. n. [from the sound mu], to mutter, mumble, speak in a low tone (poet.; syn.: murmuro, musso).

  1. I. Lit.: etiam muttis? So. Jam tacebo, Plaut. Am. 1, 1, 225; id. Mil. 2, 6, 83: inpinge pugnum, si muttiverit, id. Bacch. 4, 7, 2; id. Most. 2, 1, 54: nihil jam mutire audeo, Ter. And. 3, 2, 25: neque opus est Adeo mutito, nor should it even be muttered, be hinted at, id. Hec. 5, 4, 26: si muttivero, etiam quod certo scio, Plaut. Mil. 2, 6, 84.
  2. II. Transf.
    1. A. To bleat, as a he-goat, Auct. Carm. Philom. 58; to bark: non mutiet canis, Vulg. Exod. 11, 7.
    2. B. To creak, of a hinge: num muttit cardo? Plaut. Curc. 1, 1, 94.
    3. C. Mutire, loqui. Ennius in Telepho: palam mutire plebeio piaculum est, Paul. ex Fest. p. 145 Müll. (Trag. v. 376 Vahl.).