reservoir

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A natural or artificial pond or lake used for the storage and regulation of water.
• noun A receptacle or chamber for storing a fluid.
• noun An underground accumulation of petroleum or natural gas.
• noun A large or extra supply; a reserve.
• noun Medicine An organism or population that directly or indirectly transmits a pathogen while being virtually immune to its effects.

from The Century Dictionary.

• noun A place where anything is kept in store: usually applied to a large receptacle for fluids or liquids, as gases or oils.
• noun Specifically A place where water collects naturally or is stored for use when wanted, as to supply a fountain, a canal, or a city, or for any other purpose.
• noun In anatomy, a receptacle. See receptaculum.
• noun In botany:
• noun One of the passages or cavities found in many plant-tissues, in which are secreted and stored resins, oils, mucilage, etc. More frequently called receptacle.
• noun A seed or any organ of a plant in whieh. surplus assimilated matter (reserve material) is stored up for subsequent use.
• To furnish with a reservoir; also, to collect and store in a reservoir.
• noun In organ-building, same as storage-bellows. See bellows, 3, and organ, 6.

from the GNU version of the Collaborative International Dictionary of English.

• noun 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.
• noun (Bot.) A small intercellular space, often containing resin, essential oil, or some other secreted matter.
• noun (Med.) a large quantity of infectious microorganisms resident in animals other than man, potentially capable of being transmitted to humans.
• noun (Med.) a large quantity of infectious microorganisms or parasites resident in animals other than man, potentially capable of being transmitted to humans; especially, such organisms in animals where they do little or no harm to the host.
• noun a large supply or stock of anything which may be rapidly put to use; a reserve.
• noun (Water Works) a principal reservoir into which an aqueduct or rising main delivers water, and from which a distributing reservoir draws its supply.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun 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.
• noun A small intercellular space, often containing resin, essential oil, or some other secreted matter.
• noun A supply or source of something.

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

• noun lake used to store water for community use
• noun tank used for collecting and storing a liquid (as water or oil)
• noun a large or extra supply of something
• noun anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies