Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
fibrīnus, a, um, adj. [1. fiber; cf. bebrinus], of the beaver, beaver-: pelles, Plin. 32, 9, 36, § 110: vestis, Isid. 19, 22, 16; Plin. 32, 10, 42, § 124.