Plain English Meaning

It is the slow-speed range where flying slower needs more power, not less, because drag goes up as the airplane gets closer to its stall speed.

Full Definition

The region of slow flight, below the airspeed for minimum power required, where flying slower actually requires more power, not less. In this region, induced drag rises sharply as airspeed decreases, so maintaining altitude at a slower speed demands a higher power setting. Pitch and power roles also reverse from normal cruise: pitch primarily controls airspeed and power primarily controls altitude.

Context Anchor

Seen in slow-flight, approach, and - discussions, especially when how pitch and power together at .