Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-dīlĭgens, entis, adj., very diligent: homo, Cic. Q. Fr. 3, 5, 6.
Adv.: perdīlĭgenter, very diligently, Cic. Att. 1, 11, 1: complecti aliquid, id. Brut. 3, 14.