Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† 1. mēdĭon, ii, n., = μήδιον, a medicinal plant, Plin. 27, 12, 79, § 104.
2. Mĕdĭon, ōnis, f., a city of Acarnania, Liv. 36, 11, 10; 36, 12, 1; 44, 23, 3.
Hence, Mĕdĭōnĭus, a, um, adj., of or belonging to Medion.
Plur. subst.: Mĕ-dĭōnii, ōrum, m., the inhabitants of Medion, Liv. 36, 12, 3.