vane

noun

1. 1

   the flattened weblike part of a feather consisting of a series of barbs on either side of the shaft

2. 2

   flat surface that rotates and pushes against air or water

3. 3

   a fin attached to the tail of an arrow, bomb or missile in order to stabilize or guide it

4. 4

   mechanical device attached to an elevated structure; rotates freely to show the direction of the wind