Plain English Meaning

A device that uses the engine's exhaust to spin a small fan, which packs more air into the engine. This lets the engine make full power even when flying high, where the air is thin.

Full Definition

An engine accessory that uses energy from the engine's exhaust gases to drive a turbine, which spins a compressor that forces additional air into the intake system. The denser intake charge allows the engine to produce more power than it could when breathing naturally, and to maintain sea-level power at higher altitudes where the surrounding air is thinner.

Context Anchor

Seen in engine operation, high- , and power-setting discussions for airplanes.