flipper
/ˈflɪpə(r); `flɪpɚ/ n
1 broad flat limb of certain sea animals (not fish) used for swimming （非鱼类海生动物的）鳍状肢
Seals, turtles and penguins have flippers. 海豹、 海龟、 企鹅均有鳍状肢.
2 either of a pair of flat rubber attachments worn on the feet and used to help in underwater diving and swimming （用於潜水和游泳的）橡胶蹼, 鸭脚板.