Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Sĕgesta, ae, f. [sibilated, acc. to Fest. p. 340 Müll., on account of the omen, from Ἔγεστα], an ancient city on the northern coast of Sicily, near Mount Eryx, Cic. Verr. 2, 4, 33, § 72; 2, 3, 40, § 92; Fest. p. 340 Müll.
Hence, Sĕgestānus, a, um, adj., of or belonging to Segesta, Segestan: civitas, Cic. Verr. 2, 3, 6, § 13; 2, 5, 32, § 83: diana, id. Or. 62, 210.
Substt.
2. Sĕgesta, ae, f., v. Segetia.
Sĕgĕtĭa, ae, f. [seges], a goddess that protects the standing crops, Macr. S. 1, 16; Aug. Civ. Dei, 4, 8; called also Sĕgesta, Plin. 18, 2, 2, § 8; cf. Becker, Antiq. vol. 4, p. 15.