Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
virgultum, i, n. [contr. from virguletum, from virgula] (only in plur.),
virgultus, a, um, adj. [virgultum], full of bushes or thickets, shrubby: vallis, Sall. Fragm. ap. Serv. Verg. A. 3, 516; Sil. 12, 354.