Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prō-gnārĭter, adv. [gnarus], very skilfully, very expertly (ante-class.): prognariter armis Certare, Enn. ap. Non. 150, 6 (Ann. v. 215 Vahl.): age, indica prognariter, decisively, definitely, Plaut. Pers. 4, 4, 39 Ritschl N. cr.; cf. Non. 150, 4, and 154, 30.