Plain English Meaning
When wind is blowing across the runway, the pilot uses the controls to stop the airplane from drifting sideways or having a wing pushed up by the wind.
Full Definition
The combined use of flight controls during takeoff, landing, or taxi to counteract the effects of a wind blowing across the runway, keeping the airplane tracking straight along the runway centerline and preventing the upwind wing from lifting.
Context Anchor
Used during crosswind takeoffs, landings, taxiing, and any time wind is pushing the airplane sideways from its intended path.