Jolly Roger

noun1

1. •
   The traditional flag used on European and American pirate ships, and, more recently, by submarine crews, often pictured as a white skull and crossbones on a black field; the blackjack.

   • The Hispaniola still lay where she had anchored; but, sure enough, there was the Jolly Roger—the black flag of piracy—flying from her peak. — 1881