1. (n.)vane any of a number of blades or plates attached radially to a rotating cylinder or shaft, as in a turbine or windmill, that move or are moved by a fluid, as steam or air.
2. vane a person who is readily changeable or fickle.
1. (noun)weathervane, weather vane, vane, wind vane mechanical device attached to an elevated structure; rotates freely to show the direction of the wind
2. (noun)vane a fin attached to the tail of an arrow, bomb or missile in order to stabilize or guide it
3. (noun)blade, vane flatsurface that rotates and pushes against air or water
4. (noun)vane, web the flattened weblike part of a feather consisting of a series of barbs on either side of the shaft
Definition of 'vane'
Webster Dictionary
1. (noun)vane a contrivance attached to some elevatedobject for the purpose of showing which way the wind blows; a weathercock. It is usually a plate or strip of metal, or slip of wood, often cut into some fanciful form, and placed upon a perpendicular axis around which it moves freely
2. (noun)vane any flat, extended surface attached to an axis and moved by the wind; as, the vane of a windmill; hence, a similar fixture of any form moved in or by water, air, or other fluid; as, the vane of a screw propeller, a fan blower, an anemometer, etc
3. (noun)vane the rhachis and web of a feather taken together
4. (noun)vane one of the sights of a compass, quadrant, etc
Definitions of vane 
