Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
saeptŭōsus (sēp-), a, um, adj. [saeptum], obscure: dictio, Pac. or Liv. Andron. ap. Tert. Pall. 3 (Trag. Rel. v. 5 Rib.).
Hence, adv.: saeptŭōsē, obscurely, Liv. Andron. ap. Non. 170, 17.