The act of hooking up with, going home with, and/or having sex with an overweight, homely man/woman. Usually occurs around last call at bars, when alcohol has impaired one's judgement or severely lowered one's standards. Always leads to Morning Remorse. Occurs whenever someone's appetite for some ass exceeds their desire to conserve their reputation and self-esteem.
Did you see that chick John just left with?!
Ahh, who cares. We've all gone piggy diving once or twice.