Plain English Meaning

Using less engine power than the situation needs, so the airplane slows down, sinks, or fails to climb at the rate you wanted.

Full Definition

A power setting that is lower than required to maintain a desired flight condition, such as airspeed, altitude, rate of climb, or rate of descent. In instrument flying, underpowering produces a deviation from the target performance — most commonly a sink below the desired altitude or a slower-than-planned airspeed.

Context Anchor

Seen when discussing instrument flying power settings, especially when adjusting power to a desired , altitude, climb, or .