Lewis & Short

murmŭro, āvi, ātum, 1, and (ante- and post-class.) murmŭror, ātus, 1, v. dep. [murmur], to murmur, mutter; to rustle, rumble, roar, etc. (cf.: susurro, musso, fremo, strepo).

  1. I. Neutr.
    1. A. Form murmuro: secum murmurat, Plaut. Aul. 1, 1, 13; Varr. L. L. 6, § 67 Müll.
      Of discontented persons, to mutter, grumble: servi murmurant, Plaut. Mil. 3, 1, 149: et murmuravit omnis congregatio, Vulg. Exod. 16, 2 al.
      Of the nightingale: secum ipse murmurat, Plin. 10, 29, 43, § 82: magia carminibus murmurata, muttered, App. Mag. p. 304, 28.
      Of inanimate things, to murmur, roar, rumble: murmurantia litora, Varr. L. L. 6, § 67 Müll.: murmurans mare, Cic. Tusc. 5, 40, 116: unda, Verg. A. 10, 212: ignis, crackles, Plin. 18, 35, 84, § 357: intestina, to rumble, Plaut. Cas. 4, 3, 6.
    2. B. Form murmuror: murmurari coepimus, Varr. ap. Non. 478: populus murmurari coepit, Quadrig. ib. 7; Varr. ib. 11.
  2. II. Act., transf., to mutter or grumble at a thing: quidam tarditatem poëtae murmurari, App. Flor. p. 353 fin.