Plain English Meaning
The part of a crosswind landing after the wheels touch down, while the airplane is still rolling down the runway. The wind is still pushing on the airplane, so the pilot keeps steering with the rudder and turning the control wheel further into the wind as the airplane slows down.
Full Definition
The phase of a crosswind landing that begins after the wheels are on the runway and continues until the airplane has slowed to taxi speed, during which the pilot must continue to manage the crosswind by progressively increasing aileron deflection into the wind while using rudder to maintain directional control along the runway centerline.
Context Anchor
You encounter this during and in guidance on how to handle the airplane after in a side wind.