Lewis & Short

frontōsus, a, um, adj. [2. frons], manybrowed, having several foreheads.

  1. I. Lit., said of Janus: frontosior, Aug. Civ. D. 1, 4 fin.
  2. II. Trop., that has a bold forehead, shameless (late Lat.), Aug. Serm. in Psa. 1, 68.