Rear window and outside mirror defroster/windshield deicer (if so equipped) switch

Rear window and outside mirror defroster/windshield deicer (if so equipped) 
switch  - Instruments and controls - Infiniti QX Owners Manual - Infiniti QX

See also:

To turn the system off
Push the OFF button. ...

Emergency engine shut off
To shut off the engine in an emergency situation while driving, perform the following procedure: – Rapidly push the push-button ignition switch 3 consecutive times in less than 1.5 seconds, or – ...

Driving on snow or ice
WARNING • Wet ice (32°F, 0°C and freezing rain), very cold snow or ice can be slick and very hard to drive on. The vehicle will have much less traction or “grip” under these conditions. Try to avoi ...