Reservoir

Part of speech: noun (n.)

1. 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.

2. A small intercellular space, often containing Receiving reservoir (Water Works), a principal reservoir into which an aqueduct or rising main delivers water, and from which a distributing reservoir draws its supply.