What is yonko meaning?

Yonko is a term used in the anime/manga series, One Piece. Yonko translates to "Four Emperors" in English. They are the four most powerful and feared pirates in the world, each controlling their own crew and territory. The current Yonko are Shanks, Kaido, Big Mom, and Blackbeard. They have all lived long enough to witness and experience the “Great Pirate Era” which was ushered in by Gol D Roger. They are considered to be the strongest pirates in the New World and they have been known to clash in fierce battles, each one vying for greater power and influence. Yonko are recognized by the World Government as one of the biggest threats to their existence.