Lewis & Short

imprŏbātĭo (inpr-), ōnis, f. [improbo], disapprobation, blame (very rare): haec et ad improbationem et approbationem testium pertinebunt, Auct. Her. 2, 6, 9; Cic. Verr. 2, 3, 74, § 172: accusatoris erit, improbatione hominis uti, id. Inv. 2, 10, 32.