Definition, synonyms and related words
A larval entozoön in the form of a subglobular or oval vesicle, or hydatid, filled with fluid, sometimes found in the tissues of man and the lower animals; -- so called from the absence of a head or visible organs on the vesicle. These cysts are the immature stages of certain tapeworms. Also applied to similar cysts of different origin.
The word comes from Ancient Greek, combining aképhalos, meaning "headless," and kústis, meaning "bladder." It originally described a headless bladder.