Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
interrŏgātor, ōris, m. [interrogo], an interrogator (post-class.), Dig. 11, 1, 11, § 7: mortuorum, a wizard, Mos. et Rom. Leg. Coll. 15, 1, 2.