Lewis & Short

trīgārĭus, a, um, adj. [triga], of or belonging to a triga; used only as subst.

  1. I. trīgārĭus, ii, m., one who drives a threehorse chariot, Plin. 28, 17, 72, § 238; 29, 1, 5, § 9.
  2. II. trīgārĭum, ii, n.
    1. A. A place in which trigae (and horses in general) are trained and exercised, Plin. 37, 13, 77, § 202; cf.: trigarium τόπος, ὅπου ἵπποι γυμνάζονται, Gloss. Philox.
      1. 2. As a nom. propr., a place or square in Rome in the ninth region, Inscr. Orell. 4266.
    2. B. (Acc. to triga, II.) The number three, Mart. Cap. 7, § 733; 9, § 895.