tail
nounThe part of an animal which terminates its body behind. In many quadrupeds, the tail is a shoot or projection covered with hair. In fowls, the tail consists of feathers, or is covered with them, which serve to assist in the direction of their flight. In fishes the tail is formed usually by a gradual sloping of the body, ending in a fin. The tail of a fish may assist the animal in steering, but its principal use is to propel the fish forward. It is the instrument of swimming.