Definitions:
a small area of still water, typically one formed naturally.

(of liquid) form a pool on the ground or another surface

a shared supply of vehicles or resources to be drawn on when needed

a game played on a small billiard table using two sets of seven coloured and numbered balls together with one black ball and a white cue ball, with the aim of pocketing all one's own balls and then the black.

a group of contestants who compete against each other in a tournament for the right to advance to the next round

an arrangement, illegal in many countries, between competing parties to fix prices or rates and share business in order to eliminate competition

(of two or more people or organizations) put (money or other assets) into a common fund