Definition
The amount of engine power selected by the pilot through movement of the throttle (or power lever), expressed by a reference such as engine RPM, manifold pressure, or a power percentage, that produces the forward force driving the airplane through the air.
Plain English
How much power you have the engine producing right now, based on where you've placed the throttle.
Context Anchor
Used in attitude flying when the pilot sets power for straight-and-level flight, climbs, descents, and airspeed changes.
Derivation
Thrust comes from the Old Norse 'thrysta', meaning to push or force. The engine and propeller push the airplane forward, so the 'thrust setting' is simply how hard you've decided to push.
Why Pilots Care
The correct thrust setting keeps airspeed and altitude stable once the proper attitude is set; the wrong setting causes unwanted speed or altitude changes.
Intuition Check
Do not read thrust setting as the same thing as airspeed. The thrust setting is what the pilot selects at the engine; the airplane’s actual speed depends on that selection plus the airplane’s attitude and flight conditions.
Example Sentence 1
After leveling off at cruise altitude, the pilot reduced the thrust setting to maintain the desired airspeed.
Example Sentence 2
After leveling off, the pilot reduced the thrust setting to prevent the airspeed from increasing beyond the target cruise speed.