Anal retention is the process were someone can retain matter in thier anus. This can be liquid, they can then squirt it out like an elephants trunk.
People often attend gym sessions to build up thier anal retentiveness, thus they can hold more liquid.
Greedy people like this as they can jack all the water at a party, or other such gala occasion.(see example)
Thas my water (suuuuuuk), if you want it get it from my anus, bitch!