Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
būmammus, a, um, adj. [bu-mamma, having large breasts], of the vine, with large clusters: uva, Varr. R. R. 2, 5, 4; Macr. S. 2, 16, 7; Serv. ad Verg. G. 2, 102.