...
A specified geographical location used to define an area navigation route or the flight path of an aircraft employing area navigation.
Annex 11 also defines waypoint as a kind of significant point (see definition above).
...
In AIXM the class DesignatedPoint is used in order to model points that have an official (5 letter) designator, have specified coordinates and do not mark the position of a Navaid. This includes, but is not limited to, '"waypoints' " as many Designated Points designated points are used for purposes other than defining a RNAV route.
The SegmetPoint.waypoint attributes that allows to specify if the point is used for Area Navigation (RNAV) procedures/routes. The SegmentPoint class is a generalistaion of the TerminalSegmentPoint and the EnRouteSegmentPoint.
...