Plain English Meaning
Stopping a takeoff on the runway instead of continuing into the air, usually because something has gone wrong — most often an engine problem. The pilot has to decide quickly, because there is only so much runway left to stop on.
Full Definition
A rejected takeoff is the deliberate decision and action to abort the takeoff and bring the airplane to a stop on the remaining runway, typically in response to an engine failure, system malfunction, control problem, or any other condition that makes continuing the takeoff unsafe. The decision must be made before the airplane reaches a speed or position from which a safe stop on the remaining runway is no longer possible.
Context Anchor
You encounter this during takeoff planning, training, and pre-takeoff , especially when reviewing what to do if the engine loses during the or just after .