Lewis & Short

auxĭlĭārĭus (AVXSILIARIVS, Corp. Inscr. III. 4753), a, um, adj. [auxilium], bringing help, aiding, auxiliary (less freq. than the preceding): magis consiliarius amicus quam auxiliarius, Plaut. Truc. 2, 1, 6.
In milit. lang.,

  1. A. With milites, equites, cohors, auxiliary troops, auxiliaries (opp. legiones): miles, Asin. ap. Cic. Fam. 10, 32 fin.: cohors, Cic. Prov. Cons. 7; Sall. J. 87, 1; Auct. B. Alex. 62; Liv. 40, 40, 13: equites, Sall. J. 46, 7.
  2. B. Absol. (eccl. Lat.): assumpsit sibi auxiliarios, Vulg. Judith, 3, 8: fortes auxiliarii, ib. 1 Macc. 3, 15.