Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Sentīnas, ātis, adj., of or belonging to Sentinum (Sentis ap. Front. Colon. p. 124 Goes.; Σέντινον in Ptol. and Polyb.), a town of Umbria: ager, Liv. 10, 27, 1; 10, 30, 4; 10, 31, 12; for which, absol.: in Sentinate, Front. Strat. 1, 8, 3 Oud. N. cr.
Plur. subst.: Sentīnātes, um, m., the inhabitants of Sentinum, Plin. 3, 14, 19, § 114.