Mar·cion·ism (mär'shə-nĭz'əm) n. A Christian heresy of the second and third centuries A.D. that rejected the Old Testament and denied the incarnation of God in Jesus as a human.
[After Marcion (died c. A.D. 160), Pontic merchant and heretic in Rome.] Mar'cion·ite' (-shə-nīt') n.