Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prŏpĭtĭātōrĭus, a, um, adj. [propitiator], atoning, reconciling (eccl. Lat.): bonitas Dei, Ambros. Fug. Sec. 3, 14.
Hence, subst.: ‡ prŏpĭtĭātōrĭum, ĭi, n.