a mirror mounted on the side, windshield, or instrument panel of an automobile or other vehicle to provide the driver with a view of the area behind the vehicle.
Origin of rearview mirror
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a mirror on a motor vehicle enabling the driver to see traffic coming behind him or her
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012