Definition
The direction toward which the wind is blowing; movement or position in the same direction the wind is travelling. In flight, an aircraft is downwind when the wind is pushing it from behind, increasing its groundspeed and carrying it away from the wind's source.
Plain English
Downwind means going the same way the wind is going. If the wind is blowing from north to south, then south is downwind.
Context Anchor
Seen when discussing wind correction, ground track, and how wind affects an airplane during straight-and-level flight.
Derivation
From Old English 'dun' (down) and 'wind.' 'Down' here doesn't mean lower in altitude — it means 'in the direction of flow,' the same way water flows 'downstream.' Downwind is simply the direction the wind is flowing toward.
Why Pilots Care
Higher groundspeed shortens the time available for traffic-pattern tasks and changes the amount of drift correction needed compared with upwind flight.
Intuition Check
Do not read "downwind" as wind coming downward, or as the direction the wind comes from. Downwind means the direction the wind is blowing toward.
Example Sentence 1
The pilot noticed the airplane drifting downwind and applied a wind correction angle to stay on the road below.
Example Sentence 2
When flying downwind the pilot applies less crab angle to hold the desired ground track than when flying upwind.