Lewis & Short

pŭgĭo, ōnis, m. [root pug of pungo; cf.: pugil, pugna].

  1. I. A short weapon for stabbing, a dagger, dirk, poniard: pugio dictus est, quod eo punctim pugnatur, Paul. ex Fest. p. 235 Müll.: Caesare interfecto statim cruentum alte extollens M. Brutus pugionem, etc., Cic. Phil. 2, 12, 28: cruentum pugionem tenens, id. ib. 2, 12, 30: pugione percussus, Sulp. ap. Cic. Fam. 4, 12, 2: fodere aliquem pugione, Tac. H. 4, 29 fin.: pugione ferire, Auct. B. Alex. 52: strictis pugionibus peti, Suet. Caes. 82.
    Worn by the emperors, to denote their power of life and death, Suet. Galb. 11; id. Vit. 15 fin.; Tac. H. 3, 68; likewise by the praefectus praetorio, Aur. Vict. Caes. 13; Lampr. Comm. 6 fin.
    Worn by the chief officers in the army as a military badge of distinction, Tac. H. 1, 43; Val. Max. 3, 5, 3.
    1. B. Transf., the title of a book or roll of the names of persons proscribed by Caligula, Suet. Calig. 49.
  2. * II. Trop.: o plumbeum pugionem! O leaden dagger! i. e. O weak argument! Cic. Fin. 4, 18, 48.