Window deflector

A window deflector is mounted above the doors of some automobiles, to protect the inside of the car from rain or other precipitation in case of slightly opened windows. Additionally, it may help to prevent precipitation entering the interior in case of an opened door, e.g. dropping from the roof or directly from the air. Deflectors are also fitted to sunroofs to deviate wind.

It is also known as a "monsoonshield" or a "rain visor" (in countries without monsoon).

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Wikipedia