Plain English Meaning
A patch of air that is moving downward. When an aircraft flies into it, the aircraft tends to sink with it.
Full Definition
A downdraft is a localized column of air moving downward, often produced by sinking air in or near a thunderstorm, by air flowing down the lee side of terrain, or by cooling air descending through the surrounding atmosphere.
Context Anchor
Seen in weather, turbulence, mountain flying, and instrument flying discussions about the elevator illusion.
Derivation
From 'down' (direction) plus 'draft,' an old word for a current or flow of air (same root as a draft of air through a doorway). So a downdraft is simply a downward-flowing current of air.
Why Pilots Care
Triggers false sensations that can pilots to make incorrect .