Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Leuci, ōrum, m., = Λεῦκοι, a people of Gallia Belgica, adjacent to the Lingones, whence, perh., the mod. Liège, Caes. B. G. 1, 40, 10; Plin. 4, 17, 31, § 106; Tac. H. 1, 64.
Collect., in sing.: Leucus, i, m., Luc. 1, 424.