Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
irrĕvĕrentĭa (inr-), ae, f. [irreverens], want of due respect or reverence, irreverence, disrespect (post-Aug.): coalitam libertate irreverentiam prorupisse, Tac. A. 13, 26: juventutis, id. ib. 3, 31: adversus, fas nefasque, id. H. 3, 51: studiorum, inattention to, neglect, Plin. Ep. 6, 2, 5: irreverentia ipsius obturatio aurium, profanity, Vulg. Sir. 27, 15.