Lewis & Short

prŏ-ăvus, i (gen. plur. proavūm, Stat. Th. 10, 807), m.

  1. I. A grandfather’s or grandmother’s father, a great-grandfather (class.): pater, avus, proavus, abavus, atavus, tritavus, Plaut. Pers. 1, 2, 5; cf. id. Mil. 2, 4, 20: proavus et avus, Cic. Mur. 7, 15; cf. Dig. 38, 10, 1; 10.
  2. II. Transf., forefather, ancestor: in censurā de proavo multum cogitato tuo, i. e. of Appius Claudius Cœcus, Cic. Fam. 3, 11, 4; Curt. 6, 11, 26; Hor. A. P. 270; Ov. Am. 3, 15, 5; Stat. Th. 10, 807: felices proavorum atavi, Juv. 3, 312.