cyst Meaning, Definition & Usage

  1. noun a closed sac that develops abnormally in some body structure
  2. noun a small anatomically normal sac or bladderlike structure (especially one containing fluid)
    vesicle.

WordNet

Cyst noun
Etymology
Gr. bladder, bag, pouch, fr. to be pregnant. Cf. Cyme.
Definitions
  1. (Med.) (a) A pouch or sac without opening, usually membranous and containing morbid matter, which is accidentally developed in one of the natural cavaties or in the substance of an organ. (b) In old authors, the urinary bladder, or the gall bladder. Written also cystis.
  2. (Bot.) One of the bladders or air vessels of certain algæ, as of the great kelp of the Pacific, and common rockweeds (Fuci) of our shores. D. C. Eaton.
  3. (Zoöl.) (a) A small capsule or sac of the kind in which many immature entozoans exit in the tissues of living animals; also, a similar form in Rotifera, etc. (b) A form assumed by Protozoa inwhich they become saclike and quiescent. It generally precedes the production of germs. See Encystment.

Webster 1913