Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
imprŏbātor (inpr-), ōris, m. [improbo], a disapprover, condemner (post-class.): malorum, bonorum probator, App. de Deo Socr. p. 51: malorum, Tert. Patient. 5.