Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impĭger (inp-), gra, grum, adj. [2. inpiger], not indolent, diligent, active, quick, unwearied, indefatigable, energetic (class.; cf.: laboriosus, navus, industrius): se praebebat patientem atque impigrum, Cic. Verr. 2, 5, 10, § 27: in scribendo, id. Fam. 2, 1, 1: vir ad labores belli, id. Font. 15, 33: ceciditque in strage suorum, Impiger ad letum, Luc. 4, 798: impiger manu, Tac. A. 3, 20: mercator, Hor. Ep. 1, 1, 45: Appulus, id. C. 3, 16, 26: Hercules, id. ib. 4, 8, 30: impiger, iracundus, inexorabilis, acer, id. A. P. 121: equus, Lucr. 5, 883; Hor. C. 4, 3, 4: Jugurtha ut erat impigro atque acri ingenio, Sall. J. 7, 4: impigrae mentis experientia, Lucr. 5, 1452: impigrae linguae, ignavi animi, Sall. Or. Licin. ad Pleb. med.: militia, Liv. 3, 5, 15.
With a partitive gen.: impiger fluminum Rhodanus, i. e. the swiftest, Flor. 3, 2, 4.
With a respective gen.: Quirinus impiger militiae, Tac. A. 3, 48.
With inf.: impiger hostium vexare turmas, Hor. C. 4, 14, 22; Claud. in Ruf. 1, 240.
Adv.: impĭgrē, actively, quickly, readily: ut de nocte multa impigreque exsurrexi, Plaut. Rud. 4, 2, 10; cf. id. ib. 19: Marius impigre prudenterque suorum et hostium res pariter attendere, Sall. J. 88, 2: impigre se movere, Liv. 1, 10, 3: consulem impigre milites secuti sunt, id. 2, 47, 2: impigre promissum auxilium, id. 3, 8, 4.
Comp. and sup. in the adj. and adv. seem not to occur.