Plain English Meaning
It is a runway-by-runway calculation done in advance that tells the crew the heaviest weight they can safely take off at, and the exact path to fly if an engine quits, so the aircraft will still clear terrain and obstacles on the remaining engine.
Full Definition
A pre-computed engineering study, performed for a specific aircraft type at a specific runway, that determines the maximum allowable takeoff weight and the procedure to follow if an engine fails after V1, ensuring the aircraft can either stop on the remaining runway or continue the takeoff and clear all obstacles along a defined departure path with one engine inoperative.
Context Anchor
You will see this term in turbine and multi-engine operations when planning a takeoff from a runway that may be by , obstacles, , or engine- .