sexātrūs — Lewis & Short
sexātrūs, uum, f.sex,
I the sixth day after the Ides:
sexatrus ab Tusculanis post diem sextum Idus vocatur (dies),Varr. L. L. 6, § 14 Müll.; cf. Fest. s. v. Quinquatrus, p. 254 ib.