acanthocephalan: any of various worms living parasitically in intestines of vertebrates having a retractile proboscis covered with many hooked spines
worm: any of numerous relatively small elongated soft-bodied animals especially of the phyla Annelida and Chaetognatha and Nematoda and Nemertea and Platyhelminthes; also many insect larvae
kinematics: the branch of mechanics concerned with motion without reference to force or mass