Pronunciation: (vān),[key] —n. 1. See weather vane. 2. a blade, plate, sail, etc., in the wheel of a windmill, to be moved by the air.
3. any of a number of blades or plates attached radially to a rotating drum or cylinder, as in a turbine or pump, that move or are moved by a fluid, as steam, water, hot gases, or air.
4. a person who is readily changeable or fickle.
5. Aerospace. a. any fixed or movable plane surface on the outside of a rocket providing directional control while the rocket is within the atmosphere.
b. a similar plane surface located in the exhaust jet of a reaction engine, providing directional control while the engine is firing.
6. Ornith.the web of a feather. See illus. under feather. 7. Navig.,Survey.either of two fixed projections for sighting an alidade or the like.
8. Archery.feather (def. 5).
Pronunciation: (vān),[key] —n. Sir Henry(Sir Harry Vane), 1613–62, British statesman and author.