Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
fustĭtŭdĭnus, a, um, adj. [fustistundo], cudgel-banging, a word comically formed to indicate the place where slaves were beaten: apud fustitudinas ferricrepinas insulas, i. e. ergastula, Plaut. As. 1, 1, 21.