Lewis & Short

bīgae, ārum (in plur. through the whole ante-Aug. per.; cf. Varr. L. L. 9, 39, 142; 10, 2, 165; 10, 3, 177; Serv. ad Verg. A. 2, 272; Charis. p. 20 P.; post-Aug. also in sing. bīga, ae; so Stat. S. 1, 2, 45; 3, 4, 46; id. Th. 1, 338; Sen. Herc. Oet. 1520; Plin. 34, 8, 19, § 89; 35, 11, 40, § 141; Tac. H. 1, 86; Suet. Tib. 26; Val. Max. 1, 8; Inscr. Orell. 2545; Vulg. Isa. 21, 9; v. Neue, Formenl. 1, 462; v. also trigae and quadrigae), f. [for bijugae from bis-jugum], a pair of horses or (rarely) of other animals; also, a two-horsed car or chariot: bigas primas junxit Phrygum natio: quadrigas Erichthonius, Plin. 7, 56, 57, § 202: Rhesi niveae citaeque bigae, Cat. 55, 26: Hector raptatus bigis, Verg. A. 2, 272: et nox atra polum bigis subvecta tenebat, id. ib. 5, 721; Val. Fl. 3, 211: roseae Aurorae, Verg. A. 7, 26 al.: cornutae, a team for ploughing, Varr. ap. Non. p. 164, 23; Isid. Orig. 18, 36, 1 and 2.
Stamped on a coin, Plin. 33, 3, 13, § 46; v. bigatus.
Adj.: equis bigis meare, Manil. 5, 3.