Lewis & Short

antĕ-signānus, i, m. [signum], that is before the standard; hence,

  1. I. Lit.: antesignant (sc. milites), a chosen band of Roman soldiers who fought before the standards, and served for their defence, Caes. B. C. 1, 43; 1, 57; Liv. 22, 5; 9, 39; Varr. ap. Non. p. 553, 10.
  2. II. Transf., a leader, commander: in acie Pharsalicā, Cic. Phil. 2, 29; so App. M. 4, p. 147, 12.