Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
impĕtrĭo, no perf., ītum, 4, v. n. desid. [id.], relig. t. t., to seek to obtain through omens, to seek by consulting auspices: ut nunc extis, sic tunc avibus magnae res impetriri solebant, Cic. Div. 1, 16, 28: in impetriendis consulendisque rebus, id. ib. 1, 2, 3: qui impetrire velit, id. ib. 2, 15, 35: impetritum, inauguratum est: quovis admittunt aves, Plaut. As. 2, 1, 11.
Part. as subst.: impetrītum, i, n., a favorable auspice or omen, Val. Max. 1, 1, 1; Plin. 28, 2, 3, § 11.