Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
vōcĭfĕro, āre, 1, v. a., rare collat. form of vociferor: crescere turba et vociferare ex omnibus locis, Liv. 7, 12, 14; cf. id. 10, 28, 12, s. v. vociferor: qui vociferant saepe, Varr. R. R. 3, 9, 5.
Pass. impers.: vociferatum ferociter, Liv. 24, 21, 2.