Plain English Meaning

How much power the engine has to produce just to hold a steady speed in level flight. Less power than this and the airplane slows down or sinks; more than this and it speeds up or climbs.

Full Definition

The amount of engine power needed to maintain a given airspeed in level flight at a specific weight, altitude, and configuration. It is the power that exactly overcomes the total drag acting on the airplane at that airspeed, so the airplane neither accelerates nor decelerates and neither climbs nor descends.

Context Anchor

Seen when discussing how pitch and power control the airplane’s energy state, especially when changing speed, climbing, descending, or maintaining level flight.