Plain English Meaning

The engine is fitted with a turbocharger or supercharger that pushes extra air into the cylinders even on the ground, so it makes more power down low than a regular engine of the same size.

Full Definition

Ground boosting is the use of a turbocharger or supercharger to raise the engine's manifold pressure above standard sea-level atmospheric pressure while operating at or near sea level, producing more power than a normally aspirated engine of the same displacement could produce at that altitude.

Context Anchor

Seen in discussions of turbocharged airplane engines, settings, manifold pressure limits, and the between boosting power near the ground and maintaining power at altitude.