The Collaborative International Dictionary of English v.0.48:

Rotifera \Ro*tif"e*ra\, n.; pl. [NL., from L. rota ? wheel +
   ferre to bear.] (Zool.)
   An order of minute worms which usually have one or two groups
   of vibrating cilia on the head, which, when in motion, often
   give an appearance of rapidly revolving wheels. The species
   are very numerous in fresh waters, and are very diversified
   in form and habits.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Rotifera
    n 1: a phylum including: rotifers [syn: Rotifera, phylum
         Rotifera]