Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* tĕnē̆brĭco, āvi, 1, v. n. [tenebricus], to become dark: sol mediā die tenebricavit, Tert. adv. Jud. 13 med. ex Amos, 8, 9 (where the Vulg. has tenebrescit).
tĕnē̆brĭcus, a, um, adj. [tenebrae], dark, gloomy (very rare): nam te in tenebricā saepe lacerabo fame Clausum, Pac. ap. Non. 179, 14 (Trag. Rel. v. 158 Rib.): Tartarea tenebrica plaga, * Cic. poët. Tusc. 2, 9, 22: vestis, dark, black, Tert. Pall. 4 fin.