The Collaborative International Dictionary of English v.0.48:

Tardigrade \Tar"di*grade\, a. [L. tardigradus; tardus slow +
   gradi to step: cf. F. tardigrade.]
   1. Moving or stepping slowly; slow-paced. [R.] --G. Eliot.
      [1913 Webster]

   2. (Zool.) Of or pertaining to the Tardigrada.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tardigrade \Tar"di*grade\, n. (Zool.)
   One of the Tardigrada.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tardigrade
    n 1: an arthropod of the division Tardigrada