Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Trĕbĭa, ae, m., = Τρεβίας, ὁ (sc. ποταμός), a river in Upper Italy, celebrated for Hannibal’s victory over the Romans, now Trebbia, Liv. 21, 52 sq.; Flor. 2, 6, 12; Luc. 2, 46; Sil. 4, 495; 4, 645; 6, 707; 9, 189.
2. Trĕbĭa, ae, f., a village in Umbria, now Trevi, Arn. 3, 122.
Hence,