A Pool

1. A small and rather deep area of (usually) fresh water, as one supplied by a spring, or occurring in the course of a stream or river; a reservoir for water.
2. Any small body of standing or stagnant water; a puddle.
3. Ellipsis of swimming pool
4. A supply of resources.
5. (by extension, computing) A set of resources that are kept ready to use.
6. A small amount of liquid on a surface.
7. A localized glow of light.