Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Tīsĭas, ae, m., = Τισίας, a Sicilian who wrote on oratory, Cic. Brut. 12, 46; id. Inv. 2, 2, 6; id. de Or. 1, 20; Quint. 2, 16, 3; 3, 1, 8.