A wing was a body part that enabled flight.
There were numerous types of pterodactyls, ranging in size from small (TV: Invasion of the Dinosaurs) to ones with forty-foot wingspans. (PROSE: Blood Heat) No one knew how they took off from the ground to fly. (PROSE: EarthWorld)
Menoptera had four large wings, which allowed them to fly. If removed, the wings would quickly grow back, but the Menoptera would be unable to fly again. (TV: The Web Planet) The Second Doctor later discovered that it was the anti-gravitic power of the isocryte in the Menopteran diet that allowed them to fly. (PROSE: Twilight of the Gods)
Using the butterfly effect, an agent of the Council of Eight released a butterfly in 1588. The flapping of its wings caused a storm a week later which sank the Spanish Armada. (PROSE: Sometime Never...) The Eighth Doctor recalled a saying in the Academy about how the beat of a butterfly's wings in Mettula Orionsis caused a time storm in the Mutter's Spiral. (AUDIO: Storm Warning)
As recalled by Brother Lassar, the people of Bessan had "some rather lovely wings" which were inherited by the Krillitanes after they invaded the planet. As a result, the Krillitanes were compared to bats. (TV: School Reunion)