Plain English Meaning
The fastest speed the manufacturer recommends for normal cruise flying. You can fly slower, but you shouldn't routinely cruise faster than this.
Full Definition
The highest airspeed at which an aircraft is designed to be flown in normal cruise flight, as published by the manufacturer in the Pilot's Operating Handbook. It represents the upper limit of routine cruise operation, distinct from never-exceed speed (VNE) and maximum structural cruising speed (VNO).
Context Anchor
Seen in discussions of wing and leading-edge device behavior, especially when comparing airflow at high cruise speed with airflow at slow speed.