Lewis & Short

stădĭum, ii, n. (masc. collat. form, acc. plur. stadios, Macr. Somn. Scip. 1, 15 med.; gen. plur. usu. stadium; but stadiorum, Plin. 2, 108, 112, § 247; 4, 1, 2, § 5; 4, 12, 24, § 75), = στάδιον.

  1. I. In gen., a stade, stadium, a distance of 125 paces, or 625 Roman feet, equal to 606 feet 9 inches English; it was an eighth part of a milliarium, or somewhat less than an eighth of an English mile, Plin. 2, 23, 21, § 85; Col. 5, 1, 6; Censor. de Die Nat. 13; Cic. Fin. 5, 1, 1; id. Ac. 2, 31, 100; id. Fam. 16, 2; Sall. Fragm. ap. Non. 496, 1; Plin. 2, 21, 19, § 83; 2, 108, 112, § 247.
  2. II. In partic., a racecourse for foot-racing, of a stadium in length (among the Greeks): qui stadium currit, Cic. Off. 3, 10, 42: ut in stadio cursores exclamant, id. Tusc. 2, 23, 56; cf. Suet. Dom. 5; Eutr. 7, 15.
    1. B. Trop., a contest, = contentio (perh. only in the foll. passages): in stadium artis rhetoricae prodire, Auct. Her. 4, 3, 4: in stadio laudis versari, Rutil. Lup. 2, p. 77 (p. 139 Frotscher; but in Cic. Brut. 64, 230, the correct read. is in studio laudis).