Definition 1 of 2
Plain English Meaning
How much power the engine is making right now, set by the pilot using the engine controls. Different aircraft show this in different ways, but the idea is the same: a chosen level of engine output for a chosen phase of flight.
Full Definition
The amount of power an engine is producing at a given moment, established by the pilot through the throttle and (where applicable) propeller and mixture controls. In piston aircraft, power setting is typically expressed as a combination of manifold pressure (in inches of mercury) and propeller RPM. In turbine aircraft, it is expressed using parameters such as N1, EPR, or torque, depending on engine .