vane in WordNet English dictionary

1. flat surface that rotates and pushes against air or water
   blade  vane 
   
2. the flattened weblike part of a feather consisting of a series of barbs on either side of the shaft
   vane  web 
   
3. mechanical device attached to an elevated structure; rotates freely to show the direction of the wind
   weathervane  weather vane  vane  wind vane 
   
4. a fin attached to the tail of an arrow, bomb or missile in order to stabilize or guide it
   vane