A place where anything is kept in store; especially, a place where water is collected and kept for use when wanted, as to supply a fountain, a canal, or a city by means of aqueducts, or to drive a mill wheel, or the like.
- A natural or artificial pond or lake used for the storage and regulation of water.
- A receptacle or chamber for storing a fluid.
- An underground accumulation of petroleum or natural gas.
- Anatomy See cisterna.
- A large or extra supply; a reserve: a reservoir of good will.
- Medicine An organism or a population that directly or indirectly transmits a pathogen while being virtually immune to its effects.