Lewis & Short

per-tĭnax, ācis, adj. [tenax], that holds fast, that clings firmly, very tenacious.

  1. I. Lit. (only poet. and in post-Aug. prose): digitus male pertinax, Hor. C. 1, 9, 24: ales unguibus pertinax, App. Flor. p. 366: tenaxne pater ejus est? Ph. Pater immo edepol pertinax, exceedingly avaricious, Plaut. Capt. 2, 2, 39.
    1. B. Transf., that lasts long, very durable: spiritus, Plin. 10, 29, 43, § 81: siligo in Allobrogum agro pertinax, id. 18, 8, 20, § 85.
  2. II. Trop., firm, constant, steadfast, persevering, unyielding; in a bad sense, obstinate, pertinacious, stubborn (cf. pervicax); constr. absol., with in and abl.; also (rare and not ante-Aug.) with in and acc., adversus and acc., ad and acc.; also (post-Aug.) with gen., Att. ap. Non. 433, 6 sq.: concertationes in disputando pertinaces, Cic. Fin. 1, 8, 27 sq.: pertinacissimus fueris, si, etc., id. ib. 2, 33, 107: valde pertinax, id. ib. 2, 3, 9: pertinax fama, Plin. 24, 17, 101, § 159: studium, Quint. Inst. prooem.: certamen, Liv. 2, 40: stare pertinaci statu, Gell. 2, 1, 2: octoginta milia fortissimae pertinacissimaeque in retinendis armis juventutis, Vell. 2, 27, 1: pertinax virtus, Liv. 25, 14: pertinax adversus temerarios impetus, id. 28, 22, 14: pertinacior in repugnando, id. 29, 33: pertinax ad obtinendam injuriam, id. 29, 1, 17: in quod coepit pertinax et intenta, Sen. Ira, 1, 1, 2.
          1. (β) Poet., with inf.: fortuna … Ludum insolentem ludere pertinax, Hor. C. 3, 29, 51.
          2. (γ) With gen.: justitiae, App. Mag. p. 338, 34: irae, Val. Max. 6, 3, 3.
            Hence, adv.: pertĭnācĭter.
    1. A. Very fast or firmly, very tenaciously, persistently: haec ipsa magis pertinaciter haerent, quo deteriora sunt, Quint. 1, 1, 5; Suet. Tib. 74: pertinacius resistere, Plin. 16, 43, 83, § 227: pertinacissime retinere, id. 33, 6, 32, § 100.
    2. B. Constantly, firmly, steadily, perseveringly; obstinately, stubbornly, pertinaciously: pertinaciter liberalibus studiis deditus, Suet. Claud. 40 fin.: pertinaciter in aliquā re manere, Varr. R. R. 1, 20: pertinaciter offensus, Planc. ap. Cic. Fam. 10, 23, 1: contendere, Suet. Caes. 1: studere, Sen. Ep. 5, 1.
      Comp.: pertinacius insequi, Hirt. B. G. 8, 13.
      Sup.: pertinacissime pabulo abstinere, Suet. Caes. 81 med.; id. Ner. 56.
  3. III. Pertĭnax, ācis, m., surname of the emperor P. Helvius, who succeeded Commodus on the throne, Capitol. Pert. 1; Aur. Vict. Epit. 18.