Lewis & Short

prōsăĭcus, a, um, adj. [1. prosa].

  1. I. Prosaic, in prose (post-class.): prosaico relatu, Ven. Carm. 7, 11, 1; id. Vit. S. Mart. 1, 13.
  2. II. Subst.: prōsăĭcus, i, m., a prose writer, prosaist (post-class.), Ven. Vit. S. Mart. 2, 469.