Pĕtŏsīris, ĭdis, m., = Πετόσιρις,
a celebrated Egyptian mathematician and astrologer , Plin. 2, 23, 21, § 88; 7, 49, 50, § 160; Firm. Math. 4, praef.—Hence, transf., a great mathematician , astrologer , in gen., Juv. 6, 580.