flipper: (海豹、企鵝等海洋生物用來游泳的)鰭肢,鰭足, 阔鳍,Whales , seals , penguins , and turtles have flippers.fin: 鰭;(飛機的)翼(片);鰭狀物We could see the fin of a shark as it slowly circled our boat.