It is called the Jolly Roger
They call it the "Jolly Roger" or "Skull & Cross bones".
The Jolly Roger
jolly rogers
The Jolly Rodger
If you mean of pirate lore, it is known as the Jolly Rodger.While a pirate crew would fly the black flag to intimidate a potential ship it intended to attack, it was not the only flag used. A crew would first fly the skull and crossbones on a black background so the other ship would be intimidated, if the other ship didn't surrender the crew would lower the black flag and raise a red flag with a skull and cross bones or whatever symbol the ships crew used as a Jolly Rodger. The red flag showed the crew the time for surrender was over and now everyone on the ship would be killed. Pirates did not take prisoners nor did they spare those people that didn't surrender the first offer.
Emmanuel Wynne..................The Jolly Roger is the name now given to any of various flags flown to identify the user as a pirate. The most famous Jolly Roger today is the Skull and Crossbones, a skull over two long bones set in an X arrangement on a black field. Historically, the flag was flown to induce pirates' victims to surrender readily.
Another term for skull is cranium.
"Die schwarz rot gold"(the black red gold) is the common term used for this flag.
Occipital is the term usually used when referring to the base of the skull.
The term that means congenital fissure of the skull is craniosynostosis.
Another term for "skull" is "cranium," which refers to the part of the skeleton that encloses the brain.
The Cheyenne term for skull is seotse-meta'-eshko.