MarcionismEccl.|ˈmɑːʃ(ɪ)ənɪsm| [f.Marcion + -ism.] The doctrine of the Marcionites. 1882Salmon in Smith's Dict.Chr.Biogr. III. 821/2 If we accept this as the original form of Marcionism, Marcion owed more to the older Gnostics than we should otherwise have supposed.