Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nūgax, ācis (collat. form indecl. ‡ nugas, σαπρός, Gloss. Philox.; so, ‡ nugas, inutilis, Gloss. Vet.; cf. Don. p. 1749 P.; Charis. p. 1; 15; 22; 120 ib.; Diom. p. 286 P.; Prisc. p. 649; 701 ib.; Val. Prob. 1464 and 1478 ib.), adj. [nugor], jesting, trifling, frivolous, Varr. ap. Non. 355, 22: qui tam nugax esset, Cael. ap. Cic. Fam. 8, 15, 1: nugax es, Petr. 52; Ambros. Ep. 58, 6 ext.
Adv. only sup.: nūgācissimē (-sŭmē), in the most trifling manner, Plaut. Trin. 3, 3, 90.