Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
peccātrix, īcis, f. [peccator], a female sinner (post-class.), Paul. Nol. Carm. 28, 127; Hier. adv. Joann. Jerosol. n. 4; Vulg. Luc. 7, 39.