Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
saevĭtas, ātis, f. [saevus], rage, violence, fury (late Lat.), Prud. στεφ. 10, 483; Firm. Math. 5, 5; Ambros. in Luc. 9, § 32; id. de Spirit. Sanc. 3, 16, 117.