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Petrēĭus, i, m., name of a Roman gens.
So, esp, a lieutenant of Pompey in the civil war, Caes. B. C. 1, 38; 63; cf. Cic. Att. 8, 2, 3. He is probably the same person with M. Petrejus, lieutenant of the consul C. Antonius, who defeated the followers of Catiline at Fœsulœ, A. U. C. 692; Cic. Sest. 5, 12; Sall. C. 59, 5 sq.
Hence,
Petrĕus, a, um, adj. [1. petra or Petrus], Petrean (eccl. Lat.): istae spinae, Petra et Petro transeunte, petreis pedibus tritae sunt, of rock or stone, or pertaining to the Apostle Peter, Aug. Serm. 297, 2 fin.