Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
* sup-poenĭtet (subp-), ēre, v. n. impers., to be somewhat sorry, to repent a little: nam et illum furoris et hunc nostrum copiarum suppoenitet, Cic. Att. 7, 14, 1.