Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
actūtum, adv. [“ab actu” (as astutus from astu; or with tum as enclitic, in der Handlung da, Corss. Ausspr. II. 849), “id est, celeritate,” Prisc. 1013 P.; so Hand, s. v. who explains: uno actu, nulla re intercedente; Lindem. de Adv. Lat. Spec. 4, p. 17, regards it as formed from an obs. vb. actuo, with the meaning cum multo actu, non segniter; cf.: ait et dicto citius placat, qs. while in the act of speaking, Verg. A. 1, 142; cf. Hor. S. 2, 2, 80]; immediately, quickly, instantly (in Plaut. very often, more rarely in Ter., and, except in Cic. Phil. 12, 11, 26: Verg. A. 9, 255; Ov. M. 3, 557; id. H. 12, 207; Liv. 29, 14, 5; and Quint. 4, 3, 13, perh. not occurring in the class. per.): ite actutum, Naev. ap. Non. 323, 1: aut hic est aut hic adfore actutum autumo, Pac. ap. Non. 237, 11; Plaut. Am. 1, 1, 198: redibo actutum … id actutum diu est, id. ib. 1, 3, 32; and so id. Curc. 5, 3, 49; id. Cap. 3, 5, 75 al.: vos ite actutum, Att. ap. Non. 357, 13; Ter. Ad. 4, 4, 26; id. Ph. 5, 6, 12; often in late Lat.: si bene aestimo, actutum merebitur, Symm. Et. 1, 41; 2, 64; 3, 43; 5, 35.