reservoir

American  

[rez-er-vwahr, -vwawr, -vawr, rez-uh-] / ˈrɛz ərˌvwɑr, -ˌvwɔr, -ˌvɔr, ˈrɛz ə- /

noun

reservoirs plural

1. a natural or artificial place where water is collected and stored for use, especially water for supplying a community, irrigating land, furnishing power, etc.

2. a receptacle or chamber for holding a liquid or fluid.

3. Geology. pool16

4. Biology. a cavity or part that holds some fluid or secretion.

5. a place where anything is collected or accumulated in great amount.

   Synonyms:

   stockpile, fund, pool, store, hoard

6. a large or extra supply or stock; reserve.

   a reservoir of knowledge.

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reservoir British  

/ ˈrɛzəˌvwɑː /

noun

1. a natural or artificial lake or large tank used for collecting and storing water, esp for community water supplies or irrigation

2. a receptacle for storing gas, esp one attached to a stove

3. biology a vacuole or cavity in an organism, containing a secretion or some other fluid

4. anatomy another name for cisterna

5. a place where a great stock of anything is accumulated

6. a large supply of something; reserve

   a reservoir of talent

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reservoir Scientific  

/ rĕz′ər-vwär′ /

1. A natural or artificial pond or lake used for the storage of water.

2. An underground mass of rock or sediment that is porous and permeable enough to allow oil or natural gas to accumulate in it.

3. An organism that is the host for a parasitic pathogen or that directly or indirectly transmits a pathogen to which it is immune.

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Other Word Forms

Noun Inflected Forms

• reservoirs
  plural

Etymology

Origin of reservoir

1680–90; < French réservoir, equivalent to réserv ( er ) to reserve + -oir -ory ²

Explanation

The word reservoir refers to a place where large amounts of water get stored. It can also be used to describe great amounts of other things, such as when you refer to a trivia expert as a reservoir of useless knowledge. The word reservoir comes from the French réservoir, which further derives from the Old French reserver, meaning "to reserve." Knowing this, it makes sense that the meaning evolved into a place, either man-made or natural, where water is stored or "reserved," usually for distribution for drinking, irrigating, and generating power. Remembering the related word reserve might also help in both the spelling and pronunciation of the word, as reserve is spelled (and pronounced) with "er," the same as "reservoir."

Example Sentences

Rescuers scoured flooded parts of China for survivors on Wednesday after storms killed 17 people and caused dozens of rivers to overflow and a reservoir dam to burst, with officials warning of more rain.

From Barron's • Jul. 8, 2026

To handle the extra volume, engineers send surplus water down 5 Shaft into the deep pool below, much like an overflow spillway helps relieve pressure at a full reservoir.

From Science Daily • Jul. 6, 2026

Southern Water said investment in infrastructure, including the UK's first new reservoir for 30 years, would help stop it taking water from the Test and Itchen rivers by 2040.

From BBC • Jul. 3, 2026

Record-low snowpack across the West is lowering reservoir levels and could curb production of low-cost hydropower.

From The Wall Street Journal • Jul. 2, 2026

In the middle of the excelsior nest sat a squat, black metal machine with four blades on the front and a glass reservoir on the back into which my father poured kerosene.

From "The Evolution of Calpurnia Tate" by Jacqueline Kelly

Related Words

• basin
• cistern
• container
• lake
• pond
• pool
• reserve
• source
• stockpile
• storage
• supply
• tank