Definition 1 of 2
Definition
A waypoint or fix that an aircraft is permitted to pass abeam without overflying it directly. The aircraft begins its turn to the next leg before reaching the waypoint, so the flight path curves inside the fix rather than passing through it.
Plain English
A point on the route that you don't have to fly directly over. You start turning toward the next point a little before you get to it, so your path arcs past the waypoint instead of going right through it.
Context Anchor
Seen in GPS, RNAV, and instrument procedure discussions, especially when describing how an aircraft turns at a route point.
Derivation
Fly-by comes from the everyday idea of flying by something, meaning passing near it rather than stopping at it or going exactly through it. In navigation, that helps: the aircraft passes the point as part of a smooth turn rather than treating it as a point that must be crossed exactly.
Why Pilots Care
Allows safe visual confirmation of conditions or runway alignment before landing, or provides controlled demonstration without risk of unintended touchdown.
Intuition Check
Fly-by does not mean ignoring the point. It means the turn may be planned before the point so the aircraft stays smoothly on the route.
Example Sentence 1
Most enroute RNAV waypoints are fly-by, so the autopilot begins the turn before reaching the fix.
Example Sentence 2
During the airshow, the formation executed a precise fly-by over the crowd at 500 feet.