Official Aviation Definition
A waypoint is a designated geographical point on Earth defined by geographic coordinates (latitude and longitude). In RNAV and GPS flight planning, five-letter pronouncable identifiers (e.g., MERIT, KANNI) mark reporting points, turns along airways, and approach fixes.
In Simple Words
A digital landmark in the sky marked by GPS coordinates that airplanes fly through along their route.
Real-World Flight Example
The Boeing 787 sequenced waypoint BEBOP and initiated a 15-degree right turn along airway Jet 50.