Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dē-rĕpentĕ, adv. (qs. departing from the regular course of time), suddenly, on a sudden (mostly ante-class—for syn. cf.: desubito, subito, repente, statim, continuo, confestim, actutum, extemplo, etc.): derepente contulit sese in pedes, Enn. ap. Non. 518, 20; so id. ib. 6; Att. Afran. Turpil., Novius, Varro, Pompon. ib. 5-22; Plaut. Most. 2, 2, 57; Ter. Hec. 4, 1, 3 and 39; Poëta ap. Cic. Div. 1, 31, 66; Suet. Tib. 23; id. Vesp. 23; Tac. H. 1, 63 (in Liv. 21, 41, 6, the true reading is repente).