Plain English Meaning
The airplane wants to point its nose down on its own, so the pilot has to pull back slightly on the controls to keep it where they want it.
Full Definition
A condition in which the airplane's nose tends to pitch downward, requiring aft (back) pressure on the controls to maintain the desired pitch attitude. It commonly occurs during descents when power is reduced, as the loss of propeller slipstream over the tail and the change in trim conditions cause the nose to drop.
Context Anchor
Encountered during descents, especially after reducing power, changing speed, or adjusting the airplane for a new .