Upvote:-1
https://en.m.wikipedia.org/wiki/Waypoint calls it a leg or a stage:
[A waypoint] most often refers to coordinates which specify one's position on the globe at the end of each "leg" (stage) of an air flight or sea passage.
Upvote:2
The path which can be travelled between two waypoints (without reference to any specific flight) is an airway or air route or flight path.
When part of the flight plan for a specific flight, itβs a segment or route segment.
Note that segment has different semantics at the flight plan level compared to the use in fare rules and the like.