Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
irrīdĭcŭlum (inr-), i, n. [irrideo], a laughing-stock: irridiculo habere, to make a laughing-stock of, Plaut. Poen. 5, 4, 10: irridiculum esse, to be a laughing-stock, id. Cas. 5, 2, 3.