from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A change in wind direction and speed between slightly different altitudes, especially a sudden downdraft.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A change of wind speed, direction, and magnitude.
Sorry, no etymologies found.
But she believed him the same way she believed Air Traffic Control when they reported no wind shear and you suddenly found your aircraft dropping at three thousand feet a minute when you were only two thousand feet in the air.