Phylum or class of elongated wormlike parasites that live in the intestines of vertebrates: spiny-headed worms WordNet 3.0 & Open English WordNet

Acanthocephala is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Wikipedia

Phylum of parasitic platyzoan "worms". Wikipedia Disambiguation