A pool in which the depth of the pool indicates the health of a person's genetic background. Those who swim in the deep end of the pool generally have good and healthy genes while those who do not are over in the shallow end.

All the humans together, referring to the genes for reproduction. Mainly used for removing yourself from the gene pool, either by doing something that makes you unable to reporduce yourself, like celibaly or getting sterilized, or by getting yourself dead (in a very stupid way). Very popular on Darwin Awards.
Removing yourself from te gene pool is seen as positive evolution since you won't spread your genes anymore, which is a good thing since you are very stupid (according to the way you died).

A term to referring to very tall men. Also a theory describing how tall men date short women in order to even out the gene pool, therefore preventing their children from being amazon freaks.

Filling a persons inny belly button full of semen

When a guy ejaculates onto his stomach and the jizz slides down and wells in his belly button. Hence, gene "pool".

This is a humorous reference to the likely genetic nature of someone's problems.

Festering pool of water from which morons spring.