Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Augustīnus, a, um, adj. [Augustus], of or pertaining to Augustus: currus, the chariot of Augustus. Suet. Cland. 11.
2. Augustīnus, i, m. [Augustus], a Roman cognomen, as D. Aurelius Augustinus, St. Augustine, the greatest of the Latin fathers, A. D. 354-430; cf. Tenffel. Rom. Lit. § 434.