cyst

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. Pathology An abnormal membranous sac containing a gaseous, liquid, or semisolid substance.
• n. Anatomy A sac or vesicle in the body.
• n. Biology A small capsulelike sac that encloses certain organisms in their dormant or larval stage.
• n. Botany A thick-walled resting spore, as in certain algae or fungi.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. 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.

from the GNU version of the Collaborative International Dictionary of English

• n.
• 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 algæ, as of the great kelp of the Pacific, and common rockweeds (Fuci) of our shores.
• n.
• 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.

from The Century Dictionary and Cyclopedia

• n. In anatomy, a bladder; a large vesicle.
• n. In pathology, a bladder-like bag or vesicle in animal bodies which includes morbid matter.
• n. In zoology, a hydatid; a cystic worm, or encysted state of a tapeworm.
• n. In cryptogamic botany, a cell or cavity, usually inclosing other cells or reproductive bodies, as an envelop inclosing a group of diatoms or desmids, or a cell containing an antherozoid; in certain algæ, a sporecase. See coniocyst.
• n. Sometimes, improperly, cist.
• n. The resistant coating formed by the parent organism previous to sporulation and inclosing the spores, in Sporozoa.
• n. In Sporozoa, the common envelop surrounding the two associated gametocytes.
• n. The resistant covering secreted by many Infusoria previous to going into a resting-stage, or before fission, or for the purpose of resisting draught or other unfavorable conditions of environment.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. a small anatomically normal sac or bladderlike structure (especially one containing fluid)
• n. a closed sac that develops abnormally in some body structure