Plain English Meaning

A pump, driven by the engine itself, that squeezes more air into the cylinders so the engine can keep making strong power even when flying high where the air is thin.

Full Definition

An engine-driven air compressor that increases the pressure of the air delivered to the cylinders of a piston engine, allowing the engine to produce more power and to maintain sea-level power at higher altitudes where the air is thinner.

Context Anchor

You will see this term in discussions of piston-engine power, high-altitude performance, and engine operating limits.