Definition
Waypoints created by the pilot, rather than published on aeronautical charts, by entering specific latitude and longitude coordinates (or a bearing and distance from a known fix) into an area navigation system such as a GPS or FMS. The system stores these custom points so they can be used to build or modify a flight route.
Plain English
Navigation points that the pilot makes up and enters into the GPS or flight computer, instead of using the standard ones already printed on the charts.
Context Anchor
Seen when entering or editing a route in an onboard navigator, especially when the point you need is not already in the system database.
Derivation
“Waypoint” combines “way,” meaning a route or path, with “point,” meaning a specific place. That helps because a waypoint is not a whole route; it is one exact place along the route. “User-defined” means the user creates that place instead of choosing one that was already published.
Why Pilots Care
They provide routing flexibility for custom paths or fixes, but must be entered and verified accurately because they lack the integrity checks of database waypoints and can introduce navigation errors if misused.
Intuition Check
Do not assume a user-defined waypoint is an official or checked navigation point. It is a custom point created by the user, so the pilot must verify that its position is correct.
Example Sentence 1
The search crew programmed user-defined waypoints around the last reported position so the GPS would guide them along a precise grid pattern.
Example Sentence 2
When the destination airport was not in the database, the crew created a user-defined waypoint at its published coordinates and flew direct to it.