Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
littĕrātōrĭus (lītĕr-), a, um, adj. [litterator], grammatical: eruditio, Tert. Idol. 10.
The fem. not to be used as a substantive: grammatice litteratura est, non litteratrix, quemadmodum oratrix: nec litteratoria, quemadmodum oratoria, Quint. 2, 14, 3.