Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impī̆grĭtĭa (inp-), ae, f. [impiger], activity, indefatigableness, persistency, Ambros. de Noë, 2, 3; id. de Jacob. 2, 2, 8: impigritas pro impigritia, Non. 125, 20.