a natural or artificial lake where water is collected and kept in quantity for use by a community
a part of something, e.g. a machine, in which a liquid or gas is held
a place in which fluid liquid or gas gathers, e.g. a cavity in the body or in rock
a cavity in an organism containing a bodily fluid or secretion
an available extra source or supply
an untapped reservoir of ideas
[French réservoir from early French reserver: see reserve1]