Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
obreptīcĭus or -tĭus, a, um, adj. [obrepo], surreptitious, obreptitious (postclass.): petitio, Cod. Just. 3, 6, 3; Cod. Th. 4, 22, 6 (al. obrepta).