Definition
A named GPS/RNAV waypoint located at the beginning of the landing surface of a runway, used as the missed approach point on most RNAV (GPS) approaches with vertical guidance and as a reference for the final approach segment.
Plain English
A precise GPS point sitting right at the start of the landing portion of the runway. The aircraft's navigation system uses it as the spot where, if you can't see the runway, you must go missed.
Context Anchor
Seen on RNAV instrument approach charts at the runway end, commonly as the last named point on the final approach path before the missed approach route.
Derivation
Threshold' comes from Old English 'therscwold,' the strip of wood at the bottom of a doorway that you cross when entering. The runway threshold is the doorway into the landing surface, and the waypoint marks that doorway as a fixed point in the navigation database.
Why Pilots Care
It supplies the exact lateral and vertical guidance needed for a safe touchdown when visibility is low.
Intuition Check
Do not read threshold as a general limit or setting. Here it means the marked beginning of the runway available for landing; the waypoint is a stored navigation point at that location, not a point the pilot chooses.
Example Sentence 1
As we crossed the runway threshold waypoint without the runway in sight, I called the missed approach and pushed the throttles up.
Example Sentence 2
The pilot confirmed the runway threshold waypoint coordinates matched the chart before beginning the descent.