Source : Webster's Revised Unabridged Dictionary (1913)

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.] (Zo["o]l.)
   (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.

Source : WordNet®

armadillo
     n : burrowing chiefly nocturnal mammal with body covered with
         strong horny plates