Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mortĭfĭcus, a, um, adj. [mors-facio], deadly, fatal (eccl. Lat.): cibus, Tert. Carm. adv. Marc. 4, 5: mortifico vulnere ictus, v. l. ap. Val. Max. 5, 6, 1 (Halm).