[rez-er-vwahr, -vwawr, -vawr, rez-uh-]


a natural or artificial place where water is collected and stored for use, especially water for supplying a community, irrigating land, furnishing power, etc.
a receptacle or chamber for holding a liquid or fluid.
Geology. See under pool1(def 6).
Biology. a cavity or part that holds some fluid or secretion.
a place where anything is collected or accumulated in great amount.
a large or extra supply or stock; reserve: a reservoir of knowledge.

Nearby words

  1. reserved occupation,
  2. reserved power,
  3. reserved word,
  4. reservedly,
  5. reservist,
  6. reservoir bag,
  7. reservoir host,
  8. reservoir of spermatozoa,
  9. reservoir rock,
  10. reset

Origin of reservoir

1680–90; < French réservoir, equivalent to réserv(er) to reserve + -oir -ory2




a small body of standing water; pond.
a still, deep place in a stream.
any small collection of liquid on a surface: a pool of blood.
a puddle.
a subterranean accumulation of oil or gas held in porous and permeable sedimentary rock (reservoir).

verb (used without object)

to form a pool.
(of blood) to accumulate in a body part or organ.

verb (used with object)

to cause pools to form in.
to cause (blood) to form pools.


of or for a pool: pool filters.
taking place or occurring around or near a pool: a pool party.

Origin of pool

before 900; Middle English; Old English pōl; cognate with Dutch poel, German Pfuhl Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for reservoir

British Dictionary definitions for reservoir



a natural or artificial lake or large tank used for collecting and storing water, esp for community water supplies or irrigation
a receptacle for storing gas, esp one attached to a stove
biology a vacuole or cavity in an organism, containing a secretion or some other fluid
anatomy another name for cisterna
a place where a great stock of anything is accumulated
a large supply of something; reservea reservoir of talent

Word Origin for reservoir

C17: from French réservoir, from réserver to reserve




a small body of still water, usually fresh; small pond
a small isolated collection of liquid spilt or poured on a surface; puddlea pool of blood
a deep part of a stream or river where the water runs very slowly
an underground accumulation of oil or gas, usually forming a reservoir in porous sedimentary rock

Word Origin for pool

Old English pōl; related to Old Frisian pōl, German Pfuhl




any communal combination of resources, funds, etca typing pool
the combined stakes of the betters in many gambling sports or games; kitty
commerce a group of producers who conspire to establish and maintain output levels and high prices, each member of the group being allocated a maximum quota; price ring
finance, mainly US
  1. a joint fund organized by security-holders for speculative or manipulative purposes on financial markets
  2. the persons or parties involved in such a combination
any of various billiard games in which the object is to pot all the balls with the cue ball, esp that played with 15 coloured and numbered balls; pocket billiards

verb (tr)

to combine (investments, money, interests, etc) into a common fund, as for a joint enterprise
commerce to organize a pool of (enterprises)
Australian informal to inform on or incriminate (someone)
See also pools

Word Origin for pool

C17: from French poule, literally: hen used to signify stakes in a card game, from Medieval Latin pulla hen, from Latin pullus young animal

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for reservoir
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for reservoir


[rĕzər-vwär′, -vwôr′, -vôr′]


A fluid-containing sac or cavity.
An organism or a population that directly or indirectly transmits a pathogen while being virtually immune to its effects.
A large or extra supply; a reserve.




A collection of blood in any region of the body due to dilation and retardation of the circulation in capillaries and veins.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for reservoir



A natural or artificial pond or lake used for the storage of water.
An underground mass of rock or sediment that is porous and permeable enough to allow oil or natural gas to accumulate in it.
An organism that is the host for a parasitic pathogen or that directly or indirectly transmits a pathogen to which it is immune.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.