Lewis & Short

musso, āvi, ātum, 1, v. n. and a. (depon. collat. form: discumbimus mussati, Varr. ap. Non. 249, 10) [root mu-, shut; Sanscr. mūkas, dumb; Gr. μυάω, μυώψ; cf. μυστήριον; Lat. mutus], to say in a low tone, to mutter, murmur; to be silent respecting a thing (not in Cic. or Cæs.; syn.: mutio, murmuro).

  1. I. Lit.: mussare murmurare. Ennius: in occulto mussabant. Vulgo vero pro tacere dicitur, ut idem Ennius: non decet mussare bonos, Paul. ex Fest. p. 144 Müll. (cf. Ann. v. 185; 348; 426; Trag. v. 432 Vahl.): soli Aetoli id decretum clam mussantes carpebant, Liv. 33, 31: flent maesti mussantque patres, Verg. A. 11, 454; Anthol. Lat. 1, 170, 108: aequum non est occultum id haberi, neque per metum mussari, to bear or brook in silence, Plaut. Aul. 2, 1, 12: egomet mecum mussito: Bona mea inhiant, id. Mil. 3, 1, 118: quidquid est, mussitabo potius quam inteream, keep it to myself, id. ib. 2, 3, 40: ergo si sapis, mussitabis, id. ib. 2, 5, 67.
    Poet., of bees, to murmur, hum, Verg. G. 4, 188.
  2. II. Transf., to be afraid to say or do any thing, to be in fear or uncertainty: mussat rex ipse Latinus, Quos generos vocet, i. e. deliberates in silence, Verg. A. 12, 657: dicere mussant, id. ib. 11, 345: medici, Plin. Ep. 7, 1: juvencae, are silent, expect in silence, Verg. A. 12, 718.