The Collaborative International Dictionary of English v.0.48:

Tardigrada \Tar`di*gra"da\, n. pl. [NL. See Tardigrade, a.]
   1. (Zool.) A tribe of edentates comprising the sloths. They
      are noted for the slowness of their movements when on the
      ground. See Sloth, 3.
      [1913 Webster]

   2. (Zool.) An order of minute aquatic arachnids; -- called
      also bear animalcules, sloth animalcules, and water
      bears.
      [1913 Webster]