Origin: Greek suffix -ism
Marcionism has 2 different meanings across 1 category:
the Christian heresy of the 2nd and 3rd centuries that rejected the Old Testament and denied the incarnation of God in Jesus as a human
An early Christian following akin to but distinct from gnosticism which rejected the validity of the Old Testament and essentially denied the Trinity, regarding God the Father as an inferior demiurge, and that Jesus had nothing to do with the First Person of the Trinity.