Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Morta, ae, f., = Μορτή, one of the Fates, Liv. Andron. ap. Gell. 3, 16, 11: tria sunt nomina Parcarum, Nona, Decima, Morta, Caesell. ib.