Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
crĕper, ĕra, ĕrum, adj. [Sabine; kindr. with Sanscr. kshapā, night, and Gr. κνέφας], dusky, dark; hence, trop., uncertain, obscure, doubtful, wavering (ante- and post-class.), Varr. L. L. 6, § 5; 7, § 77; cf. Non. p. 13, 15 sq.; Paul. ex Fest. p. 52, 18 Müll.