Definition 1 of 2
Plain English Meaning
Normalizing means using a turbocharger just to keep the engine making the same power it would make at sea level, even as you climb into thinner air. It is not about boosting power above normal — it is about not losing power as you go up.
Full Definition
In a turbocharged engine, normalizing is the use of the turbocharger to maintain sea-level manifold pressure as the airplane climbs, compensating for the natural drop in atmospheric pressure with altitude. A normalized (or altitude-turbocharged) engine does not produce more than its sea-level rated power; it simply preserves that power up to a critical altitude, above which manifold pressure begins to fall.