Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
stuppĕus (stūpĕus), a, um, adj. [stuppa], made or consisting of tow: vincula, Verg. A. 2, 236: retinacula, Ov. M. 14, 547: verbera fundae, Verg. G. 1, 309: flamma, burning tow, id. A. 8, 694: messis, i. e. flax, Grat. Cyn. 36.