Lewis & Short

ĕpīstŏlĭcus, a, um, adj., = ἐπιστολικός, pertaining to or consisting of letters, epistolic: Epistolicae Quaestiones, the title of a work of Cato, Gell. praef. § 9; 7, 10, 2; and of Varro, id. 14, 7, 4; 14, 8, 2.