Lewis Short
(adjective) : sub-dĭālis (subdīvālis, Amm. 19, 11, 4), e, dius
* That is in the open air (post-Aug.): inambulationes,Plin. 14, 1, 3, § 11: petrae,id. 34, 12, 29, § 117.—As subst.: subdĭālĭa, ĭum, n., open galleries or terraces; a transl. of the Gr. ὑπαίθρια, ὕπαιθρα, Plin. 36, 25, 62, § 186.—Also in sing.: subdival domus,Tert. adv. Jud. 11.
Charlton T. Lewis, Charles Short, A Latin Dictionary