Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-caedo, cĕcīdi, caesum, v. a., to cut up completely = ad internecionem caedere (post-class.): exercitum, Flor. 3, 20, 10. (dub.; al. cecidit): terga hostium, id. 4, 12, 7.
per-cīdo, cīdi, cīsum (perf. percecīdi, Flor. 4, 12, 7), 3, v. a. [caedo], to beat or cut to pieces, to smash.