Lewis & Short

1. brūtus, a, um, adj. [kindr. with βᾰρύς, perh. contr. from barutus, a lengthened form of barus, like actutum, astutus, cinctutus, versutus, from actu, astus, cinctus, versus; cf. also βρῖθύς, heavy, weighty; Fr. and Engl. brute, brutal].

  1. I. Lit., heavy, unwieldy, immovable (rare): brutum antiqui gravem dicebant, Paul. ex Fest. p. 31 Müll.: pondus, falling down with heavy weight, Lucr. 6, 105: tellus, * Hor. C. 1, 34, 9 (cf.: terra iners, id. ib. 3, 4, 45: immota tellus, Sen. Thyest. 1020: terra semper immobilis, Serv. ad Verg. A. 10, 102: Unde Horatius. Et bruta tellus): corpora neque tam bruta quam terrea, neque tam levia quam aetheria, App. de Deo Socr. p. 47, 5.
  2. II. Trop., dull, stupid, insensible, unreasonable.
    1. A. Of men: brutum dicitur hebes et obtusum … Pacuvius Hermiona: et obnoxium esse aut brutum aut elinguem putes, Non. p. 77, 31 sq.: fortunam insanam esse et caecam et brutam perhibent philosophi, Pac. ap. Auct. Her. 2, 23, 36: quod bruti nec satis sardare queunt, Naev. ap. Fest. s. v. sardare, p. 322 Müll. (Bell. Punic. v. 65, p. 18 Vahl.): T. Manlius relegatus a patre ob adulescentiam brutam atque hebetem, Sen. Ben. 3, 37, 4; App. M. 7, p. 191, 30: homo, Lact. 7, 4, 12; Prud. στεφ. 2, 66; cf. 2. Brutus, II. B.
      Esp. in a play on the name, 2. Brutus, v. h. v.
    2. B. Of animals, irrational ( = ἀναίσθητος, Arist. Part. Anim. 3, 4) (so several times in Pliny the elder): animalium hoc maxime brutum (sc. sus), Plin. 8, 51, 77, § 207; 9, 29, 46, § 87; 11, 37, 70, § 183; 11, 39, 92, § 226.
      But only late Lat. as a general designation of animals opp. to men, our brute, irrational, dumb, Greg. Mag. in Job, 10, 13, 23; 17, 30, 46 al.
    3. C. Of inanimate things: bruta fulmina et vana, ut quae nulla veniant ratione naturae, qs. striking blindly, Plin. 2, 43, 43, § 113: scitum Caesaris, thoughtless, inconsiderate, Prud. στεφ. 5, 66.
      * Sup., Jul. Val. Rer. Gest. Alex. Magn. 3, 67.