Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
concŭpiscentĭa, ae, f. [concupisco], an eager desire, longing, concupiscence (late Lat.), Tert. Res Carn. 45, id. Anim. 16 al.; Hier. Ep. 63, 1; Paul. Nol. Ep. 30, 3.