Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
plumbōsus, a, um, adj. [plumbum], full of lead, having much lead mixed with it (postAug.): plumbosa molybdaena, Plin. 34, 18, 53, § 173.
Sup.: faex plumbosissima, Plin. 33, 6, 34, § 103.