Definition
On a flight management system or GPS navigation display, the distance still to fly along the current leg of the programmed route — that is, from the aircraft's present position to the next waypoint defining the end of that leg.
Plain English
How far you still have to go before reaching the next waypoint on your route.
Context Anchor
Seen on IFR navigation displays and moving-map pages while following a route, arrival, or approach segment.
Derivation
A 'leg' in navigation is one segment of a route, from one waypoint to the next. The term comes from the older sense of a leg as a single stage of a journey. 'Remaining' simply means what is left. So 'leg remaining' = how much of the current segment is left to fly.
Why Pilots Care
Supports situational awareness for fuel management and timing of upcoming course or altitude changes.
Intuition Check
Do not read LEG REMAINING as the distance left in the entire flight. It means the distance left on the current route leg only, usually to the next waypoint.
Example Sentence 1
With twelve miles of leg remaining, the pilot began briefing the approach for the next waypoint.
Example Sentence 2
With three minutes leg remaining, the pilot began the descent checklist.