Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ălīso or Ălīson, ōnis, m., = Ἄλεισον, Ptolem., a fortress built by Drusus near the present Wesel, now Liesborn, Vell. 2, 120; Tac. A. 2, 7; cf. Mann. Germ. 81; 433.