Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
circumcīsĭo, ōnis, f. [circumcido], a cutting around, circumcision, physical and moral (only in eccl. Lat.): carnis, cordis, spiritūs, Lact. 4, 17, 1 sqq.; Tert. adv. Jud. 2; 3 et saep.