Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭbulcus, i, m. [from sus; formed in analogy with bubulcus], a swine-herd, Varr. R. R. 2, 4, 14 and 20; Mart. 10, 98, 10; Verg. E. 10, 19 Wagn. (al. bubulci).