The Collaborative International Dictionary of English v.0.48:

Acanthocephala \A*can`tho*ceph"a*la\, n. pl. [NL., from Gr. ? a
   spine, thorn + ? head.] (Zool.)
   A group of intestinal worms, having the proboscis armed with
   recurved spines.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Acanthocephala
    n 1: phylum or class of elongated wormlike parasites that live
         in the intestines of vertebrates: spiny-headed worms [syn:
         Acanthocephala, phylum Acanthocephala]