Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† mĕtaplasmus, i, m., = μεταπλασμός, a grammatical change, irregularity, metaplasm, e. g. in declension (post-Aug.): metaplasmus enim, et schematismos et schemata vocamus, Quint. 1, 8, 14; Mart. Cap. 3, § 326.