bambu;5274550 said:Oceanic ;5274439 said:wing
One of a pair of movable organs for flying, as the feather-covered modified forelimb of a bird or the skin-covered modified digits of the forelimb of a bat.
http://www.thefreedictionary.com/wing
1a : one of the movable feathered or membranous paired appendages by means of which a bird, bat, or insect is able to fly; also : such an appendage even though rudimentary if possessed by an animal belonging to a group characterized by the power of flight b : any of various anatomical structures (as of a flying fish or flying lemur) providing means of limited flight
http://www.merriam-webster.com/dictionary/wing
Your definition fails to describe the Fuegian Steamer Duck......
Wikipedia ;5274439 said:a flightless waterfowl, who has allegedly killed adults of various other waterfowl species with their powerful, spurred "wings".......
Through adaptation, thanks to evolution, the duck's wings, previously used for flight, serve the newer purpose: swimming.