echinococcus, n. [NL., fr. Gr. 'echi^nos hedgehog, sea urchin + ko`kkos grain, seed, berry. So called because forming little granular bodies, each armed with hooklets and disposed upon the inner wall of the hydatid cysts.].
A parasite of man and of many domestic and wild animals, forming compound cysts or tumors (called hydatid cysts) in various organs, but especially in the liver and lungs, which often cause death. It is the larval stage of the Tænia echinococcus, a small tapeworm peculiar to the dog. The adult form is not found in man. [1913 Webster]