Definition
A pre-takeoff ground check in which the engine is operated at a specified higher RPM to verify that the engine, magnetos, propeller, carburetor heat, and associated systems are functioning correctly before flight.
Plain English
A check done on the ground where the pilot brings the engine up to a set higher power setting and goes through a list of tests to make sure everything is working before taking off.
Context Anchor
Used during the before-takeoff check, usually in the run-up area or another safe place near the runway before the airplane lines up for departure.
Derivation
From the verb phrase 'to run up,' meaning to bring something up to a higher level or rate. In this case, the engine is 'run up' to a higher RPM than idle so its behavior under load can be observed.
Why Pilots Care
Reveals engine or system problems on the ground where they can be corrected without risk to flight safety.
Intuition Check
A run-up is not the takeoff roll, and it does not mean racing the engine without purpose. It is a controlled checklist check while the airplane is held in place.
Example Sentence 1
After taxiing to the run-up area, the pilot held the brakes, advanced the throttle to 1,700 RPM, and began the run-up.
Example Sentence 2
During the before-takeoff check the student verified that magneto RPM drop stayed within limits during the run-up.