Lewis & Short

vexillum, i, n. [dim. of vēlum], a military ensign, standard, banner, flag.

  1. I. In gen., Caes. B. G. 6, 36; Cic. Phil. 2, 40, 102; 5, 11, 29; id. Att. 10, 15, 2; id. Agr. 2, 32, 86; Tac. A. 1, 20 al.
  2. II. In partic., a red flag placed on the general’s tent, as a signal for marching or for battle: vexillum proponere, to raise or display, Caes. B. G. 2, 20: vexillo signum dare, id. B. C. 3, 89 fin.
    1. B. Transf., the troops belonging to a vexillum, a company, troop, Liv. 8, 8; Tac. H. 1, 70; Stat. Th. 12, 782.
  3. III. Trop.: Fortunae, Stat. S. 4, 2, 43.