Plain English Meaning
Take some of the lifting work off the wing by easing forward on the controls so the wing isn't being asked to lift as hard.
Full Definition
To reduce the aerodynamic load (lift force) on the wing by decreasing the angle of attack, typically through forward pressure on the controls. This lowers the wing's lift production and reduces the structural load factor, allowing the airplane to be maneuvered without exceeding stall angle of attack or structural limits.
Context Anchor
Used in spiral dive recovery and other unusual-attitude recoveries when the airplane is descending fast and the wing may be under heavy .