Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prŏpĭtĭātor, ōris, m. [propitio], a propitiator (eccl. Lat.): habentes propitiatorem dominum nostrum Jesum Christum, Hier. Ep. 21, n. 2; Ambros. in Luc. prol. 7.