The phrase "rear defroster" refers to a device in a car that helps remove frost or ice from the back window, making it easier to see through. Full definition
Options: Rear View Camera Cruise Control Auxiliary Audio Input Alloy Wheels Overhead Airbags Traction Control Side Airbags Air Conditioning Abs Brakes Power Locks Power Mirrors Am / Fm Stereo Rear Defroster Cd Audio Power Windows Cloth Seats Automatic Transmission Bluetooth (austin-tx.americanlisted.com)
As for the tops, those were fully lined and had glass rear windows with rear defrosters. (autobytel.com)
We tried a few more commands such as, «Air conditioner on / off», «rear defroster on / off», and «fan speed, up / down.» (cnet.com)