Lewis & Short

2. armātus, ūs, m. [armo], armor (only in the abl.).

  1. I. Lit.: haud dispari, Liv. 33, 3: Cretico, id. 42, 55 fin.: armatu sustinendo assueti milites, Fronto, Prim. Hist. Fragm. 2, p. 341.
  2. II. Meton., armed soldiers (cf. armatura, I. B.): gravi armatu, with the heavy-armed, Liv. 37, 41: magnā parte impedimentorum relictā in Bruttiis, et omni graviori armatu, id. 26, 5.