Longman Dictionary of Contemporary English
Wiktionary
n. Either of a pair of mirrors on the sides of a car or other vehicle that enable the driver to see to the side and behind.
Wikipedia
A wing mirror, also known as the fender mirror, door mirror, or side view mirror, is a mirror found on the exterior of motor vehicles for the purposes of helping the driver see areas behind and to the sides of the vehicle, outside of the driver's peripheral vision (in the ' blind spot').
For mirrors on bicycles and motorcycles see " Rear-view mirror".
Although almost all modern cars mount their side mirrors on the doors, normally at the A-pillar, rather than the wings ( fenders – portion of body above the wheel well), the "wing mirror" term is still frequently used.
The side mirror is equipped for manual or remote vertical and horizontal adjustment so as to provide adequate coverage to drivers of differing height and seated position. Remote adjustment may be mechanical by means of bowden cables, or may be electric by means of geared motors. The mirror glass may also be electrically heated and may include electrochromic dimming to reduce glare to the driver from the headlamps of following vehicles. Increasingly, the side mirror incorporates the vehicle's turn signal repeaters. There is evidence to suggest mirror-mounted repeaters may be more effective than repeaters mounted in the previously predominant fender side location.