tank used for collecting and storing a liquid (as water or oil)
lake used to store water for community use
anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies; "an infectious agent depends on a reservoir for its survival"
a large or extra supply of something; "a reservoir of talent"
an organization (usually with a commercial bank) that is engaged as a trustee or fiduciary or agent in handling trust funds or estates of custodial arrangements or stock transfers or related services