Lewis & Short

2. circumflexus, ūs, m. [circumflecto],

  1. I. a bending round, a vault, arch: mundi, Plin. 2, 1, 1, § 1: caeli, id. 6, 34, 39, § 212.
  2. II. A winding, circuit: qui (Tanais) per sinuosos labitur circumflexus, Amm. 22, 8, 27.