Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impĭĕtas (inp-), ātis, f. [impius], want of reverence or respect, irreverence, ungodliness, impiety, undutifulness, disloyalty (rare but class.): nihil est quod tam miseros faciat quam impietas et scelus, Cic. Fin. 4, 24, 66; Ov. M. 4, 4: impietatis duces, of disloyalty, treason to one’s country, Cic. Lael. 12, 42: impietatem punire voluit (legum lator), i. e. undutifulness to parents, Quint. 7, 1, 52; Suet. Vit. Luc.; cf. Ov. M. 8, 477: Albucilla defertur impietatis in principem, of high-treason, Tac. A. 6, 47; Plin. Pan. 33, 3.