Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Leucŏpĕtra, ae, f., = Λευκοπέτρα (white rock), a promontory in the territory of the Bruttii, near Rhegium, now Capo dell’ Armi, Cic. Phil. 1, 3, 7; id. Att. 16, 6, 1; 16, 7, 1.