A / ătăvus
noun

ătăvus

gen. ătăvi · gender masculine · decl. 2nd
(archaic, ), , at avus
the father of a great-great-grandfather; great-great-grandmother
the father of a great-great-grandfather (abavus) or great-great-grandmother, opp. to adnepos.
Lit., cf. Dig. 38, 10, 1; 38, 10, 10; Isid. Orig. 9, 5, 9 and 10; 9, 6, 23 and 25; Plaut. Pers. 1, 2, 5; Cic. Cael. 14.—
forefather
In gen., sometimes, like avus, abavus, etc., for ancestor, forefather: Turnus avis atavisque potens, Verg. A. 7, 56: Evocat antiquis proavos atavosque sepulchris, Ov. Am. 1, 8, 17: Maecenas, atavis edite regibus, Hor. C. 1, 1, 1.