Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Grādīvus (once Grădīvus, Ov. M. 6, 427), i, m. [perh. from gradior, he who steps forth, marches out], a surname of Mars: (Numa) Salios item duodecim Marti Gradivo legit, Liv. 1, 20, 4: rex Gradive, Verg. A. 10, 542: Nymphas venerabar agrestes Gradivumque patrem, id. ib. 3, 35: Homericus, Juv. 13, 113: jure venis, Gradive, Ov. F. 2, 861; Juv. 2, 128; so absol.: Gradivus, id. ib. 3, 677; 5, 556; id. M. 14, 820; 15, 863.