SQUID MARK
A mark often left on the front of a pair of underwear, usually the result of leftover male ejaculate.
After a pleasurable night of adultery with my wife's sister, the only evidence that got me busted was a couple of overlooked squid marks on my boxers, and her dress.
Squid Marks
Another name for a person's tattoos.
"Check out the squid marks on that guy! That is some serious ink!"