Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prae-formo, āvi, ātum, 1, v. a., to form or fashion beforehand, to instruct beforehand, to prepare, etc. (post-Aug.): his praeformat dictis, Sil. 7, 385; Tert. Apol. 1 fin.: velut praeformata materia, Quint. 2, 6, 5: praeformatae infantibus litterae, traced beforehand, id. 5, 14, 31.