A bezoar (ˈ) is a mass found trapped in the gastrointestinal system (usually the stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

), though it can occur in other locations. A pseudobezoar is an indigestible object introduced intentionally into the digestive system.

There are several varieties of bezoar, some of which have inorganic constituents and others organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

Bezoars were sought because they were believed to have the power of a universal antidote
An antidote is a substance which can counteract a form of poisoning. The term ultimately derives from the Greek αντιδιδοναι antididonai, "given against"....

 against any poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....