Lewis & Short

Marcĭon, ōnis, m. (Marcīon, Prud. Ham. 120),

  1. I. a heretic of Sinope, who gave himself out to be Christ, Tert. de Praescr. adv. Haeret. 30; Prud. Ham. 502.
    Hence,
    1. A. Marcĭōnensis, e, adj., of or belonging to the heretic Marcion: continentia, Tert. Praescr. Haeret. 30.
    2. B. Marcĭō-nista, ae, m., a follower of the heretic Marcion, a Marcionite.
      Plur.,       Cod. Just. 1, 5, 5.
    3. C. Marcĭōnīta, ae, m., for Marcionensis, of or belonging to the heretic Marcion: Marcionita Deus, tristis, ferus insidiator, i. e. feigned by Marcion, Prud. Ham. 129.
      Plur.: Marcĭōnītae, Marcionites, disciples of Marcion, Tert. Praescr. Her. 49; Lact. 4, 30, 10; Ambros. de Fide, 5, 13, 162.
  2. II. A native of Smyrna, the author of a treatise De simplicibus effectibus, Plin. 28, 4, 7, § 38.