Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
infīdigrăphus, a, um, adj. [vox hybr., infidus- γράφω], writing faithlessly (eccl. Lat.): infidelis Deo nec infidigraphus nec ingratus, (Hilar.) Anon. in Job, 1, 124.