Definition
The direction from which the wind is blowing, or movement against the wind. In flight, an upwind heading or upwind leg means the airplane is pointed into the wind.
Plain English
Upwind means facing into the wind, or the side that the wind is coming from.
Context Anchor
Used when describing wind drift and the correction needed to keep the airplane moving along the desired path over the ground.
Derivation
From 'up' (toward the source) plus 'wind.' Just as 'upstream' points toward where a river starts, 'upwind' points toward where the wind starts.
Why Pilots Care
Choosing an upwind heading allows the pilot to counteract crosswind drift and hold the intended course without lateral deviation.
Intuition Check
Upwind does not mean higher in altitude. Here it means toward the source of the wind, not upward in the sky.
Example Sentence 1
On the upwind leg after takeoff, the pilot held a slight crab to stay aligned with the runway centerline.
Example Sentence 2
On the upwind leg the airplane flies directly into the wind before turning crosswind.