On a male, it's the prime real estate at the base of you ballsac up to your o ring. On a female, the juiciest region of exploration from the south side of the snapper to the start of her bunghole.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.