Real Dictionary

wing
countable noun: The wings of a bird or insect are the two parts of its body that it uses for flying.

wing in American English
either of the two feathered forelimbs of a bird, fully developed for flying, as in most birds, or insufficiently developed for flight and used for balance in running, etc., as in chickens or ostriches, or for swimming, as in penguins or some ducks
noun: either of the two forelimbs of most birds and of bats, corresponding to the human arms, that are specialized for flight

wing in British English
noun: either of the modified forelimbs of a bird that are covered with large feathers and specialized for flight in most species