Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
infernas, ātis, adj. [infernus], of or from the lower country, lowland (rare): abies, Plin. 16, 39, 76, § 197; Vitr. 2, 10: navicularii, Inscr. Orell. 1084: terra, Mart. Cap. 6, § 603.