Definition 1 of 2
Definition
A pre-takeoff ground check in which the pilot increases engine power to a specified RPM and verifies that the engine and its systems are operating correctly. The check typically includes testing each magneto individually, checking carburetor heat, confirming proper oil pressure and temperature, and verifying that the engine produces the expected static RPM.
Plain English
A test you do on the ground before takeoff: you push the throttle up to a set RPM and check that the engine, ignition, and instruments are all behaving normally.
Context Anchor
You encounter this during pre-takeoff procedures, usually in a run-up area near the departure end of the runway.
Derivation
From the everyday phrase 'to run something up,' meaning to bring it up to speed. In aviation it became the name for bringing the engine up to a higher power setting briefly to test it.
Why Pilots Care
Detects engine or system problems on the ground where they can be safely addressed instead of discovering them after takeoff.
Intuition Check
Do not read run up as simply “speeding up.” In aviation, a run up is a deliberate engine check done on the ground before takeoff.
Example Sentence 1
After taxiing to the run-up area, she completed the engine run up and confirmed both magnetos were within limits.
Example Sentence 2
During the run up the right magneto showed a 125 RPM drop, well within the allowable limit.