cyst
A pouch or sac without opening, usually membranous and containing morbid matter, which develops in one of the natural cavities or in the substance of an organ.
Word history
From Ancient Greek "κύστις" (anatomical sac).
Where this comes from
This definition is adapted from “cyst” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.