DEFINITION
CYST:
• (n.) A pouch or sac without opening, usually membranous and
containing morbid matter, which is accidentally developed in one of the
natural cavities or in the substance of an organ.
• (n.) In old authors, the urinary bladder, or the gall bladder.
• (n.) One of the bladders or air vessels of certain algae, as of
the great kelp of the Pacific, and common rockweeds (Fuci) of our
shores.
• (n.) A small capsule or sac of the kind in which many immature
entozoans exist in the tissues of living animals; also, a similar form
in Rotifera, etc.
• (n.) A form assumed by Protozoa in which they become saclike and
quiescent. It generally precedes the production of germs. See
Encystment.