Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prŏpĕrus, a, um, adj. [root par-, to make; whence parare, parĕre], quick, speedy, hastening (mostly poet. and in postAug. prose): properam pro celeri ac strenuā dixisse antiquos, testimonio est Cato, Fest. p. 253 Müll.: properi aurigae, Verg. A. 12, 85: Telamon, Ov. M. 7, 647: pede, Cat. 62, 34: gressus, Val. Fl. 4, 176: spe ac juventā properus, Tac. H. 4, 68: agmen, id. ib. 4, 79: sibi quisque properus, each one hastening for himself, Tac. A. 1, 65.
With gen. (Tacitean): Agrippina oblatae occasionis propera, quickly seizing the proffered occasion, Tac. A. 12, 66: irae, id. ib. 11, 26: vindictae, id. ib. 14, 7.
With inf. (Tacitean): quoquo facinore properus clarescere, Tac. A. 4, 52.
Hence, adv., in two forms.