Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Lissus, i, f., and Lissum, i, n., = Λισσός, a city in southern Dalmatia, on the borders of Macedonia, now Alessio, Caes. B. C. 3, 26, 4; Plin. 3, 22, 26, § 144; Liv. 43, 20; 44, 30.