Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impollūtus (inp-), a, um, adj. [2. inpollutus], unstained, unpolluted (post-Aug.): fides, Sil. 13, 679: virginitas, Tac. A. 14, 35: intemeratus, impollutus, id. ib. 16, 26.