The Collaborative International Dictionary of English v.0.48:

Armadillo \Ar`ma*dil"lo\ ([aum]r`m[.a]*d[i^]l"l[-o]), n.; pl.
   Armadillos (-l[=o]z). [Sp. armadillo, dim. of armado armed,
   p. p. of armar to arm. So called from being armed with a bony
   shell.] (Zool.)
      (a) Any edentate animal if the family Dasypid[ae],
          peculiar to America. The body and head are incased in
          an armor composed of small bony plates. The armadillos
          burrow in the earth, seldom going abroad except at
          night. When attacked, they curl up into a ball,
          presenting the armor on all sides. Their flesh is good
          food. There are several species, one of which (the
          peba) is found as far north as Texas. See Peba,
          Poyou, Tatouay.
      (b) A genus of small isopod Crustacea that can roll
          themselves into a ball.
          [1913 Webster]