Plain English Meaning

When something has gone wrong and a pilot needs to fly lower than normally allowed, the controller uses a special map showing terrain and tall obstacles, and gives the pilot headings and altitudes that keep the aircraft safely away from them.

Full Definition

A service in which an air traffic controller provides radar headings and altitude information to a pilot in distress, using an Emergency Obstruction Video Map (EOVM) to keep the aircraft clear of terrain and obstructions during an emergency that requires descent below the minimum vectoring altitude.