One Piece Encyclopedia

Yagara Bull They are the animals that are used in Water 7 like transport to cross their chanals.
Yarukiman Mangrove The Yarukiman Mangrove is a concentration of 79 mangroves, each one forms a small numbered island called "Grove" and together they form the Sabaody Archipelago.
Yonkou Yonkou or the "Four Emperors" is the name that is given to the four piratas that controls the second half of the Grand Line.
Yonshiki "Yon-shiki" (4-arts) is a variant of the Rokushiki used by the CP 9 members. As its name indicates the Yonshiki consists in the domination of four of the six techniques of the Rokushiki. The techniques that includes the Yonshiki are: Soru, Geppou, Kamie and Rankyaku. The Yonshiki is used by Nero, the novice of the CP 9.
Yubashiri "Snow Run" - Yubashiri is a sword that the owner of Loguetown wepon store gives to Zoro for free. It is a sword of the legacy of the family of the store. The grip is black and the sword is very light. It is one of the "50 Ryou Wazamono".
Yuki Onna Monet's nickname, literally "snow woman". A woman shaped spirit from the Japanese folklore that manifests on a snowy night.