Lewis Short
mĕtaplasmus (noun 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.
Charlton T. Lewis, Charles Short, A Latin Dictionary