weather vane

noun

a device, as a rod to which a freely rotating pointer is attached, for indicating the direction of the wind.

Also, weathervane.

Also called vane, wind vane.

Origin

1715-25

Examples from the web for weather vane

The weather vane spins on a rod and points in the direction from which the wind comes.
The final effect was stately: a white building with a blue and white cupola topped by a weather vane.
Therefore, after liftoff he allowed the aircraft to weather vane toward the irrigation pipes.
Aside from the weather vane, his only known weather instrument was the thermometer.

British Dictionary definitions for weather vane

noun

a vane designed to indicate the direction in which the wind is blowing