‖ metaplasisBiol.|mɛˈtæpləsɪs| [mod.L., after G. metaplase (Haeckel 1866), a. Gr. µετάπλασις, n. of action f. µεταπλάσσειν: see prec.] Haeckel's term for the middle or adult period of ontogenetic development: correlated with anaplasis and cataplasis. 1888Hyatt in Proc. Boston Soc.Nat.Hist. XXIII. 405.